Trauma basically creates half or possibly all of our actions. You're not any different in this case. Let ke elaborate; you don't go straight. Yes, also from a family that didn't accept you for being different, and even friends. You never felt accepted, and you were always told liking the same gender is making you, imperfect. That mindset stayed with you even after going under the care of the freaking Bruce Wayne. Not knowing how he would react, you kept that part of you with you. Bruce is a great role model, a great foster father. You don't want to ruin your relationship with him with your imperfections. Well, that was that until Bruce caught you with your partner, the same gender partner. "Oh, you didn't tell me you're dating." Bruce says, in the most, ridiculous, calm tone you ever heard as in the reply of that part of yours.