I'm a 59 y/o guy who is, among other things, bisexual.  I was born into an Irish Catholic family, the 4th of 5 kids, the 3rd of 3 boys.  Sadly, the stereotype of "Irish Catholic" fit my family.  Dad was an alcoholic, in the days when there was much less medical and social understanding of the disease that it was and the instablity it created in us, the children.
When I was about 10, my mother had had it.  She took 4 of us and moved into a one bedroom apartment.  She'd always worked, and in that as well as her courageous decision to leave my father, she was a woman ahead of her time.  As a Catholic, she remained married to my father until the day he died and then remained single until she died 24 years later.
My sexual awakening came roughly about the time I reached what the Catholic Church termed "the age of reason", viz. the age of 7.  I found my Dad's porn stash, a collection that for the most part would rate a borderline R in today's world.  What turned me on were the women's breasts, which was all these photos showed.  I did come across a deck of cards that had very explicit sexual activity, but that was too much for me at that age.  As many men know, boys are able to masturbate to an non-ejaculatory orgasm.  Once I discovered this pleasure and the photos and mental images of women that fed it, I was hooked.  And that was tough for a Catholic boy, because masturbation was a mortal sin, i.e., a sin which required confession for it to be forgiven and if you died with unrepentant mortal sin "on your soul" then you went straight to hell, where masturbating minors served eternal life along with the likes of Hitler, Judas, and pretty much everyone who wasn't a Catholic.
The guilt that I felt was a two edged sword.  On the one hand, I was terrified as I stood in the confessional line on Saturdays.  On the other hand, the forbidden nature of masturbation enhanced its allure and, I think, the pleasure as I passed that "point of no return" and headed to orgasm.
As I moved into adolescence, my fantasies began to mirror something that I felt in real life, namely an attraction to certain boys.  I wouldn't call it sexual but it certainly fit what today is called a "man crush".  My crushes became part of my masturbatory, but not as my sexual partners.  These boys became the sexual partners of the women in my fantasies.  And yes, there were women, not my peers.  The women were Hollywoood stars or models or even -hint to my age here - the hot girls from American Bandstand.
In high school, I desperately wanted a girl friend.  Again, I didn't have so much a sexual need as an affective one.  Of course in any situation that lent itself to fooling around with a girl, I never hesitated.  But, until the last few weeks of my senior year, I had no luck with girls when it came to having a girlfriend.
Another thing that happened in high school that affected my confidence regarding my attractiveness to girls were several same sex experiences.  The first occurred when I was 13, when another school mate felt me up in a movie theater. It was a wonderful experience and I would've gone further if the kid had wanted to.  Despite my Catholicism, I didn't feel guilty about this incident, perhaps because the other boy had initiated it.  And, I soon forgot what had happened; this was not a "gateway incident" that led to an adolescence filled with same sex encounters. The other 3 experiences were also initiated by other males, one who was a good friend (mutual j/o) and two which were unwelcomed sexual encounters with older males.  I won't go into what happened or why I call them unwelcomed, but those who have had those kinds of experiences will understand and will understand the toll they take on a person.

For reasons that are better left to my memoirs, I entered a religious order when I graduated high school.  I was 17, Vietnam was raging, I came from a poor, dysfunctional family and the Brothers offered an opportunity to get a second chance at family life, along with a good education and a teaching career.
I had no conscious awareness that there may have been a sexual component to entering the Brothers.  But I soon found out that others in my class certainly had that.  During the first year, Novitiate year, I was approached by a peer who said we could do it just once before we took vows and then that would be it.  I vacillated on this, first saying no, then saying yes, then saying no again.  The final no came right after this kid flashed his rather sizeable penis at me in the bathroom one day.  Whatever was in my head that led me to even consider sex with him was frightened out of it when I saw what he was packin!  There was another more discreet suggestion from one of the older guys in our class, but I managed to steer things away from any mention of sex between us.  That didn't deter the guy.  In the following years, he would come on stronger and stronger until one night in college, he cornered me and began to force himself on me.  I managed to summon up the courage to stop him and ordered him out of my room.  When I told the Brother Director what had happened, he said "You shouldn't have let him into the room." 
The Brother Director said this because he himself had manipulated some of his charges into a sexual relationship.  I was one of his "boys", my head so screwed up at what was happening with him that I actually took what he said and blamed myself for the repulsive behavior of the Brother who'd tried to force himself on me.
Now. lest you think I was a total innocent, I had begun to have a sexual relationship with another young Brother, of my own age, a few years before the above incident.  The Director knew about this relationship, and he actually encouraged it, using 60s-speak to make it seem perfectly okay.  I'm not blaming him that I had the consensual relationship with my "lover", but I later saw that his approval was part of his conscious or unconscious plan to get me into a vulnerable position that he could exploit.  I learned that I was not the only student Brother who was in this predicament.  As my college years went on, I had other consensual same sex encounters with my peers.  I don't know that I can justify any of this for a person who had a vow of chastity, i.e., abstinence, but all I can say was that I was an 18, 19, 20 year old with a healthy sex drive and a green light by my Director to indulge it.
For the most part, all the sex came to an end when I graduated college and went to "community" to teach.  However, I developed a serious drinking problem, owing in part of my DNA and upbringing, in part to my repressed anger at having been manipulated by the older Brothers and by my own sense that I had been weak and cowardly.
I taught as a Brother for 10 years, finally developing a bleeding ulcer as a result of my drinking.  During my stay in the hospital, I came to terms with the fact that I had to leave the Brothers. 
My thoughts on leaving were that I was going to make up for lost time as far as sexual intercourse with women went.  I was 27 and technically a virgin, at least as far as heterosexual intercourse went.  I wanted to put distance between myself and the Brothers and considered that my same sex experiences were really the result of having a sex drive and having only other males around, sort of like prison homosexuality.
Well, I found that I wasn't the hot guy I'd hoped to be.  In addition, having decided to abandon teaching along with the Brothers, I was out of work for over a year.  Eventually, I began to go downtown to the gay bars.  I had very little money at the time and I had brought my drinking under control for the time being.  Eventually, I made contact with a former Brother, a guy I'd liked although not a sexual partner.  He invited me to something called Dignity, a group of Catholic gays and their supporters.  About 6 months later, still out of work, I met a 21 year old guy (I was 28 by this time) and we clicked.  He was just finishing up college and had an apartment near the university and invited me to move in with him.  Soon after that, my gay friend let me know that there was an opening at a Catholic high school.  I applied, interviewed and got the job.  I was 28, living and having sex with a hot 21 year old, identifying myself as gay and now I was teaching at an all girls Catholic high school.  It was there that I realized that I was, indeed, bisexual.  I didn't have any sexual relationships with any students, not for a lack of trying in one case.  But I was very turned on by some of the older girls.  There's something about a Catholic high school girl in a uniform!
My relationship with my lover lasted almost 3 years.  It had become apparent that I had lots of things to work out, while he had happily come to accept himself as gay.  We parted as friends, he met a very nice guy about a year later and they have been together for the past 25 years.  I continue to "live gay" for the most part, although I had several one nighters with women.  But eventually, between my resumed drinking and the increasing sense of being a misfit in the gay community, I made some changes.  I transferred to a new school, having made a determination earlier in the year that I was going to find a partner, and I was using that term not as it is used in the gay community today but as it would have been understood in the early 1980s: a woman with whom I shared interests, values and goals, along with, of course, an unambiguous sexual attraction.  I met that woman at my new school and with in a year we were married.  I had given her my whole history, as I have told it thus far here, and she was amazingly accepting.  She'd dated a lot of men (we were in our 30s) and more than one had confessed to having had same sex experiences.  My new "girlfriend" believed that most men were probably bisexual.  And if there weren't bisexual, well then it was that they had to put that "thing" into something every chance they could!  By the way, she wasn't anti sex.  We had great sex before we got married and it honestly got better after we got married.
Within 6 years of our marriage, we'd co-created two daughters, had moved into a new house, and I had left teaching to try my hand in the "real world."  I never did quite catch my balance or find my place in that "real world". I bounced from job to job, many of them very good paying jobs.  I was drinking heavily and as time went on I felt this increasing rage and sense of entrapment.  The rage was not about my wife or kids, nor did I feel trapped in my marriage.  I was simply lost in the fallout from a shaky family foundation and undealt with anger over what had happened at the hands of my Brother Director.
Finally, 9 years into the marriage, I sought help.  The psychologist had the wisdom to realize that I wasn't going to get anywhere until I stopped drinking, and he insisted I get sober before any therapy could begin.  Having arrived at the point of "suicidal ideation", I quit drinking that day, went to AA that night and worked an outpatient program at a private clinic.  I had some brief slips over the next two years and eventually I gave up on AA, since one of my issues was, naturally, God's indifference to me while I was in the Brothers.  Rationally, I knew God had nothing to do with what happened, but I was not really rational at this point in my life.  But I was able to stop drinking, continue in therapy and, after a period of resistance, accept that I was clinically depressed and would need medicine.  It was not all roses after that, however.  With sobriety comes awareness of why I was drinking, and with that awareness comes a lot of emotion.  I actually became more volatile in the early years of sobriety and it took its toll on my family life.  After 18 years of marriage, we separated.  My kids were happy, because now there would be no fighting parents.  They still loved me but as my older daughter who was 15 at the time told me: "There's nothing worse than parents fighting."  I knew that from my own experience and regrettably I had outdone my parents in that department.
I went on a mini gay sex binge in the first months that I was living on my own again.  Although my attraction to women remains, I felt that I could not get into any relationship with a woman again, because I had no desire to "share" the fact of my bisexuality with another woman.  Towards the end of our time together, when it was apparent that we were on the rocks, I cheated on my wife with other men.  I'm not proud of that, but it revealed to me that I was capable of that and I didn't want to get into a life of deception and lies again.  I wouldn't mind a couple one night stands, if that were clear from the beginning, but there's something in me that seems to want more than that, even though I wont deny that I still have basic sexual needs.  I guess after 18 years of a relationship in which the sex was, during our best years,  an expression of and a deepening of a love we had for each other.
It's been 6 years since we separated.  At first, I thought that it would be temporary but I now see that that was born of my fear of being alone.  It's been a pretty dark 6 years for the most part, and I won't say that I see a light at the end of the tunnel.  The most I can say is that I've come to see, with a lot of help, that pretty much everything in this world is passing.  I guess my being bisexual might reflect that transience and change more than if I were absolutlely gay or straight.  Beyond the sexual attraction, there is that thing called love.  It comes in many forms, and for me it's the love I have for my best friend who is my soon to be ex-wife and for my daughters.  Yes, I have one or two friends and I cherish them.  Whatever way love comes into one's life, I think it's the one thing that, with some care, can last a lifetime.