Hi, I'm Ed and now 22, when I was growing up with my sis Ally who is 2 years younger we did some pretty wierd stuff and now I worry about it. We were close as sister and brother and really comfortable around eachother and even naked as teens but never when our parents were around. We had a family pool and spent ages in it, when Ally was 12 she started to sprout and I was awestruck by her body and often beat off thinking of her and using her underwear. In the pool we'd often mess about and I would get serious hard ons whcih I knew she felt sort of by accident a few times. Sometimes we would play a game where I would hold her under her arms and lift her up out of the water and then back down ducking her under it, as I did this I would sometimes feel up her boobs and her hard nipples, sometimes I would hold her by her waist and give her a wedgie with her swimsuit, sometimes I would have my hands on her thighs doing it and rub around her crotch area and a few times I actually cum in my trunks while we did this. She asked me to play this game and never complained where my hands were, a few times I put my fingers right on her sex and felt it through her swimsuit. My sister is now living with another girl in a full gay relationship and I fear I made her like this.
Ed, it sounds like you and your sister had some fun as siblings and taught each other a few things about sexual feelings in a subtle way. We should be comfortable in our sexuality, no matter our ages, but the expression of it with another must be with full permission. That sounds like the case, in your interactions with her, so no harm done that I can see.
Nothing that you did or didn't do with your sister would cause her to become a lesbian or bi-sexual. Her sexual preferences and desires are born within and anyone who is part of the gay-lesbian community will tell you that. You can "make" someone change their inherent sexual preferences or "unmake" them, either. They are who they are and all they want is to be accepted for who they are and for what their choices are in partners.
She kept choosing to interact with you in sexual ways, which in my mind might have spurred her onward into transitioning into a heterosexual relationship with a guy, because it was so fun being with you. You gave each other some stimulating sexual experiences which is just a part of the sexual development of each one of us. We are sexual beings and part of the balance of life is to be able to express that and feel those feelings without guilt or disapproval from others. As long as both parties are in agreement and no one gets hurt in the process, you should feel free to do as you please. There are consequences for sexual behaviors that do cause harm, emotionally or physically. STDs and pregnancy can be real-life experiences and consequences of sexual acts, when you are not entering them with clear knowledge and truthful communication.
I don't see anything to be worried about or ashamed of in your message/question here. It was just part of your transition into adulthood. I'm sure your sister feels the same way. If she is happy in her relationship she might be grateful to you for helping her open up to her own sexuality in a safe environment with her loving brother.
Time to release your fears/worries about Ally and focus on who you are and how you want to express yourself sexually with others of your choosing. Give thanks to an open and loving sister for your own awakening.