I didn’t say that clearly.
He needs to consult a lawyer for the other 2 - the argument (no idea if there have been other cases) is that since he isn’t considered their father for immigration purposes, can he still be considered their stepfather (which is what he was before)? As their stepfather, he can sponsor them.
The mother can sponsor them BUT the
19 year old has accrued unlawful presence and the 17 year old too by the time she files for them so cannot adjust in the U.S. and subject to ban. As children of LPR, they are not forgiven for overstay (which they would be as children of USC).
He needs a lawyer, fast. And file i130 and i485 for the wife and youngest child.