If I adopted a child do the parents still have to pay child support?

No.

Once you adopt the child it's your child, the parents no longer have any obligation to that child.

You will be responsible for paying to support the child. You will be the parent.

I don't know where you live and if there are laws there that are different than the norm, but generally speaking, no, they don't. When you adopt a child the child is considered yours and you support it.

Hugs, Christine