Re: Should my fiance come out as bisexual to my family? Or? What?
OK now that I have some terms for some of the stages in the spectrum from homo to hetero, then your fiancé should not come out as bisexual to your family as that would be confusing. He should come out as a biromantic homoflexible (just to make it less confusing) cheating male who helped to break up a family and slept with another biromantic homoflexible who is married and has children (just as your fiancé is about to be - married with children). At the same time he should own up to and apologise for his bad behaviour and not hide behind the fact that he was only 16 or 18 when it suits him (and apparently you too) yet is grown up enough to be in a serious relationship when it suits him.
And yes I must commend the way you have stood up to us all with unregulated wiki quotes and placing blame on the previous generations (my, oh how original) - my kids went through this although they are now in their mid 20s and are starting to take responsibility for what they need to do going forward (as I am sure you will as a mature responsible parent).
The bottom line is that your fiancé did something bad, your parents found out and suddenly you think that by coming out as bisexual or whatever, that is going to explain why he slept with a married father ? Think about this carefully and try and work out the basic morality that needs to apply. Stop blaming others for his bad behaviour - he needs to own it and apologise and then work on improving himself.
This is my quest, to follow that star
No matter how hopeless, no matter how far
To fight for the right, without question or pause
To be willing to march into Hell, for a Heavenly cause