MY son is not divorced from his wife but she took the two babies and sent them to another state to live with her birthfather while she still lives in this state with her boyfriend. Can my son go and get the kids and bring them back?

He should get an attorney. Without knowing a lot of the facts in this case, I'd say his paternal rights are still in tact and she has no right (unless there has been a judgement made in a court of law, even then, he would have rights to visitation) to withhold his children from him, especially if he is paying child support.
I would not recommend him just going and getting the kids for fear of a mess of red tape and possible kidnapping charges (yep even though they are his kids, you never know from state to state what the laws are). I wonder if he would be able to file a petition against her for taking the chidren across state lines without his consent? Again... I'd advise him to get an attorney or at least seek legal aid.

I believe the answer is yes. He will need to have birth cirtificates with his name on it, and also contact the local police in the area where the children are at. Have the police go with him. If there is no court order giving custody to the mother, and if he is on the birth cirtificate, to show his rights, then the police should be on his side.

There is no guarantee the children will be there when he arrives, so it may be a wasted trip.

If there is any court order related to him having custody, or any thing like that, then I would advise him to contact an attorney. Of course that might not be a bad idea anyway.

He may want to have it documented that he had to go out of state to get the children after she sent them there. He would also want to file for custody and try to get her to have only supervised visits for fear that she might do this type of thing again.

Does the wife have full custody of the children? Has any separation orders been issued? Any restraining orders filed? All of that would need to be considered to know for sure.