And if they have had a child here, that child is a US citizen. Do the parents have to leave and the child stays here.
Logistically and politically, that's never going to happen. Would you want to be the President who ordered the National Guard to round up illegal women and children at gunpoint?
What we can do is basically three-fold:
1) Shore up border security to minimize the flow of illegals over the border;
2) Focus heavily on assimilating all immigrants, whether legal or illegal, who are already here. Grant illegals some sort of amnesty conditioned upon them registering and passing citizenship courses etc.
3) Fine the hell out of any company that employs illegals. The dirty little secret that conservatives don't want to admit is that business owners, the vast majority of whom are Republicans, are the main reason illegals are here- the only reason there is a supply of illegals is because there is a demand for their services.