The son either should be held accountable for his mother coming here illegally or he shouldn’t.
God would not him accountable, but you would. Says a lot...
Suffering for the sins of ones father is not the same as not being allowed to benefit from the sins of ones father. To allow him to stay would be to allow him to benefit from his father’s sins.
As far as ‘being held accountable’ goes, those are your words, not the Bible’s. But, accepting that it’s wrong to hold a child accountable for the sins of his parents, sending the child back to his parent’s country of origin is not equivalent to ‘holding him accountable’. Nobody is blaming the child for what his parents did. It is simply a matter of correcting a situation that resulted from an illegal act. The intention is not to punish the child, but to enforce the conditions on immigration that we as a nation have the right to hold. The child may suffer in some ways for returning to his parent’s country or he may end up actually being happier there. Who can say? The intention, certainly, isn’t to ‘make him suffer’.
A good analogy would be if I were a car dealer, and one day a guy plunks down $100,000 for a corvette. A week later the cops show up and inform you that the guy who bought the car had just robbed a bank, and the money he paid with was stolen money. They return the car to you and ask you to give them the money so it can be returned to its rightful owner. Are you being made to suffer or are you just being asked to right a wrong that you became involved with to no fault of your own. Do you have a right to keep the money just because you didn’t commit the crime?