I'm ready for a divorce

So I don't even know how to began this story but here's a little backstory my supposed to be husband( he don't deserve the title of my husband) his dad haves alot of children and we were told he had 2 missing children's somewhere so recently 1 reached out and she came to meet them and my husband is 25yrs and she is 19yrs old and he began texting her I saw it as him getting to know his new found little sister I met her she came spent this night with us and our kids she ate my food in my fridge I welcomed her with open arms as a sister in law and comes to find out on Christmas Day they been secretly trying to have a relationship behind my back he told her he will leave us for her his family 6 kids and wife for his sister which is sick ASF and not only that he threw away 8yrs I'm definitely getting a divorce I just needed somewhere to vent bc I wasted 8yrs ans he cheated every last one and now with his sister is even more crazy 🤦🏿‍♀️💯