A similar thing happened to me when I was 16. I was at a family Christmas party and my cousin came up to me and said "I'm adopted just like you." I thought it was a joke so I went to my father and said with a smile on my face "dad, I'm not adopted right?" My father said no and that was that.

Later that night my mother and stepfather came into my saying that they needed to talk to me. I had no idea what about, because I had brushed off that comment so quickly that it wasn't even in my mind. Turned out that my father wasn't my father.

The same question kept repeating in my mind over and over 'what am I?' Eventually it came to me (and this has proven true as my life continued) that I am me. I may not share the same genes as my father, but I am the sum of all the teachings that they poured into me growing up.

When I tell this story the inevitable question always comes up "have you ever tried to reach your biological father?" Yes, he wants nothing to do with me. I am strangely fine with that. Instead of being brought up in a home with a dad who didn't want me, I got to grow up with two fathers (dad and stepdad) that adored me.

Now I say this like it was happy ending, and maybe it was, but it wasn't a happy story. I really dislike besmirching my dead father's name, but in the interest of honesty and relateability I am going to do so. My father cheated on my mother when I was 6 years old. He fell in love with the babysitter and booted us (mother, brother and I) out on Christmas day so that they could have the apartment to themselves. It was years after that that my father wanted anything to do with me or my brother. In the meantime my mother had gotten into an abusive relationship and I felt like her sole protector (imagine trying to protect your mother from being attacked with a wooden broom handle with only your 7 year old body). It wasn't until my stepfather came into the picture that my dad realized that he screwed up and wanted to be part of our lives. And while yes the story had a happy ending where I had two fathers that adored me; I only had one that taught me to do the right thing no matter how hard it is.

The best thing you can do is to stick by your mother. Not only is she going through some stuff and need your support, she's the one that is sticking by you. You're going to get through this.