I 16 f have divorced parents (mom 35 dad 38) and they both have 50/50 custody I am also the only child between them.They divorced when i was 9 and Short after the divorce my dad remarried to my stepmom(34) I’m 16 now, when my dad remarried I gained 3 step siblings that I love being a big sister too. About 2 years ago I was staying the night at my uncles in my dads sides house and hanging out with my cousins and my uncle got drunk and told me that my dad cheated on my mom with my stepmom. I was so upset and he told me that my youngest step siblings (8m&8f twins) were my half siblings and my mom found out about my dad’s other family. I was so upset and uncomfortable and I didn’t know what to do or say. I had my mom come pick me up and by the time I got home I was in tears. I told my mom what my uncle told me and she broke down and told me that my mom and dad were having trouble having a baby and my dad got stressed and angry and found my stepmom and decided he as wanted a new life with her (she also knew he had a family she was one of my moms friends)I was so upset my mom called my dad and told him what happened and him and my uncle got into a fight. After that I didn’t feel a bond with my stepmom anymore I still love my siblings though after that situation my mom introduced me to my now stepdad (36) and they are now married. Last month my dad and stepmom sat me and my siblings down and they told us they were pregnant I told them congratulations but I wasn’t as happy as the rest of my siblings were I was actually kinda mad. A week later I was at my mom’s and she told me she was pregnant I was really happy for her and my stepdad. When I was back with my dad I was also happy planning the gender reveal party for my mom and she ask me what I was doing and I told her and she said nothing and went in her room later that night my dad came in and told me that my stepmom was really upset about what I said and I should apologize and plan there gender reveal as well I told him that I had nothing to apologize for and if she didn’t break up our family by being a home-wrecker I would be happy for them and want a relationship with her. Me and my dad got into a fight and I ended up say something I regret and left and went to my moms. My mom told me I should apologize because she more happy with my step dad I tried to text my dad but he blocked my number you and if he doesn’t unblock me to talk I thinking about asking my mom to file for full custody. AITA for this I don’t think I am side note I wrote this 3 weeks ago my dad still hasn’t talked to me but I’ve been at his house.I wastalking with my bf and he told me to post it and get some opinions yes I do know what I said was bad and I kinda feel bad but I don’t wanna apologize AITA EDIT: thank you all for your opinion I feel like I only took so much out on my stepmom because she influenced him to do it I really do like hanging out with my step-siblings and I wish I could have the same relationship with her but telling them how I feel won’t go well and my dad isn’t a therapy type I do value your opinions about my relationship with my stepmom but if you were in my shoes you would see how hard it is to accept this also seeing your mom go through this is heartbreaking.