They're not his, big surprise. However, the only reason he never found out is because he was too much of a pushover to stand up to his wife. ≫Him, believing that they were his, was fine with being a completely absent father. It got so bad that they didn't even recognise him. And he blames the daughters for not recognising him, lol. That's like 80% the b*tch's wife fault, but as I said, he is at fault, too. When the revenge is said and done, he abandons them without a second thought. If it wasn't because he was a spineless wimp, maybe those kids could've met their actual fathers and have some chance at life. But in the end, they didn't do anything to him and paid the price for their mother's sluttiness and their cuck father's lack of a spine.

He uses the goddesses' powers to make the wife ret*rded. Same for the guy she cheated on him with. It's so brutal that it's pretty much akin to death. He makes them unable to talk and function. It's like turning them into mental patients, but the wife keeps her sanity. It's brutal, but underwhelming. The author chose brutality over cleverness. I once read a similar story in a manhwa where the wife is briefly shown at the end begging for scraps. This, much, much tamer revenge was infinitely more satisfying.