Hi, my husband is not sure if a set of fraternal twins are his, my first question is where does he go for a blood test?

Delaware law would control, so I can't advise you on their procedures. When they are visiting, he can go to a private lab, like Quest, to get a paternity test. He can also buy a test kit at major pharmacies and do the testing at home and send the swabs to the lab.   Delaware would control custody of the children.