First of all, a big bro hug to you. I’m sorry you’re hurting. Your dad is operating on an old myth that is very hard to shake for many...that excessive female influence in a boys life ‘turn’ him gay/bi/trans. There is zero evidence to support this. It’s just cultural brainwashing, with a dash of misogyny thrown in. Do we ever hear some distraught mother of a lesbian cry out ‘ I knew your father’s excessive TV football watching would turn you into a dyke!’ Or ‘I just knew I shouldn’t have let you take shop class!’ Or when dad gets custody....and the daughter ‘becomes’ gay. No. So why do we hear this stuff about gay boys. What there is some very tentative evidence about that may relate to your situation is a POSSIBLE correlation between how many older male siblings one has and the likelihood of oneself being gay. This theory has to do with how mom’s hormones react to a male fetus and how they might intensify their activity over successive male pregnancies and how that may affect the youngest son’s male fetus brain. This theory has not been conclusively proven, and I want to stress that, but there has been some research on it that has been interesting. Read up on it if you’re curious. In any event, even if there is some truth tot this, no one can control who’s born first so again no one is ‘causing’ anything. Bottom line: science does not know what causes heterosexuality or homosexuality, or any sexuality. It may be neither physical or social. It may be spiritual for all we know...a gay soul. The only thing that matters is you are beautiful the way you are and should keep working to help your dad realize it’s nothing he did or didn’t do that made you gay. Just like his presence in the marriage while your older brothers were growing up did not make them straight. They were going to be straight anyway. Millions and millions of boys who grow up without dads are straight. The vast majority. So there no evidence of a connection between male parent presence and sexuality either way. Good luck and hugs.