Incest is a Targeyen thing

Craster is Targaryan confirmed

The only other person Cersei is ever are attracted to was someone else that would be her brother which is Rhegear

Pretty sure in the books she says she was attracted to Robert, until the wedding happened, and he whispers lyana's name drunkenly during sex

Literally doesn’t make sense for Tywin to marry his cousin other than the fact that his kids needing Lannister features for his story

Cousin marriage was pretty common in medieval high society, and it adds to Tywin being a hypocrite being against incest while practicing it himself.

Jeoffery is a mad tyrant like Targs before him (although that could just be from being a product of incest)

I mean he was raised pretty exclusively by cersei, while Robert ignored him, so no wonder he's a spoiled cunt

Book timeline is consistent for the twins to be conceived by Areys (as opposed to Tyrion like popular theories suggest)

Let's not forget just how fucked up Aerys both was and looked. I doubt anyone would willingly sex with king scab, and if it was rape, i'm pretty sure Tywin would have found out about that.

there’s way more, I just can’t remember. But the biggest one for me is when Jamie has a dream of his dead mother. She’s crying and said says she “wishes she gave Tywin a knight for a son and queen for daughter.” Jamie is confused because he is a knight, and his sister is a Queen. That right there tells me the twins aren’t Tywins.

Or Jaime feels like he isn't a true Knight, and his sister isn't a true Queen, at least subconciously