My dad married my half-sister.....

**Edit: this is a throwaway account. I don't want to be associated with this post. Also, I'm doing this for the catharsis....**<br><br>I'm 14, and have been single-handedly raised by my birth mum (27F) since I was a toddler. She's an amazing woman, who sacrificed a lot to give me the best life possible. She's been my best friend, and confided in me about a lot of things... including our family history.<br><br>My mother was in a relationship with my birth father when she was 19, and he cheated on her when she was 20. He never knew she was pregnant, and I was born when she was 22. He never acknowledged me as his daughter, and has never had contact with us.<br><br>About 6 months ago, I started acting out. I started smoking weed, and developed an interest in vulgar hip-hop and rap music. My mum never judged me, but she had concerns, and opened up to me about my dad. She said she didn't want to deprive me of a father, and that maybe it's time for me to see the bigger picture. I don't get along with my dad's family... however, I decided to "make amends" with them... <br><br>I made contact with my dad's sister (44F) and she was really nice. I then made contact with my dad's mother (68F), and she was very concerned. She said she didn't want me to contact my dad's wife, because she didn't take kindly to "those things" and that I should only communicate with her through my aunt. I understood, and followed her instructions.<br><br>Last week, I got a call from my grandma saying she had something important to tell me, and that she needed to see me. I couldn't go, so my mum said she'd go, and that I should come with her. We went, and were greeted by my aunt, uncle (42M) and grandma. My mum excused herself to the kitchen, and my aunt and uncle said they needed to tell me something. They said my birth father is married to my older half-sister (25F). I didn't know how to react.. and my dad walked in.<br><br>The sight of him sickened me. He looked really old, and wrinkly. I never thought I'd be in the same room as him, and seeing him face to face was the most terrifying thing I've experienced. I don't get along with his family, because they "gossiped" about my mum, and blamed her for his infidelity. They are the reason I grew up without him, and my mum grew up without a family.<br><br>I'm so confused, and I don't know what to feel. My mum took me and my dad aside, and started arguing with him. He said that he considers my half-sister his daughter, and that he married her to "restore the family". My mum was angry, and said she should never have given him a second chance. I was terrified, and fled the house. I never want to see him again, and I'm so grossed out. My mum is the most beautiful woman in the world, and she's the only person I want in my life.<br><br>Can anyone relate to this?<br><br>**Edit: I feel the need to explain, because some people seem to be confused.** <br><br>* My dad committed infidelity while he was dating my mum <br>* He cheated on my mum with a woman I'll refer to as "A" (my half-sister's mum)... and "A" was already pregnant with his child at the time <br>* My mum gave birth to me, and my dad married "A" when my half-sister was 5<br>* He raised my half-sister as his daughter, and never acknowledged me as his child <br>* My half-sister has been raised to believe he's her biological father, and that my mum murdered their unborn child (exaggeration and understatement are not my strong suits) <br>* My dad and my half-sister got married when she turned 20, and the marriage was arranged by his new mother-in-law (my half-sister's maternal grandma)<br>* My dad's family never acknowledges me as his biological daughter, and they don't want my mum to be a part of our lives <br>* My dad's mum is the one who told me about his marriage, and it has been a family secret for years