wait if they share the same father aren't they half brothers?

someome pls confirm.

I think their parents just get remarried to each other

but didn't it say somewhere that (i forgot his name but the short cute one)'s mom died and his dad took him in?

ok so Sui used to live with his mom, when she died he moved in with his dad that was married to nichan's mom

It was explained in the first chapter. Both parents are divorcees and had a child in their previous marriage. The sons aren't related by blood