Our SIL who is a brilliant dad reacted in a very strange way to the birth of their son (our first grandchild.) While he was happy to help with all the chores he became withdrawn and unwilling to share the baby - he would scowl if anyone dared to pick him up. We wondered if he was jealous or wanted to keep grandparents at arm's length but it turned out the poor lad was still in shock as DD had haemorrhaged after the delivery and it was a very scary time. You say your DIL had a difficult labour so maybe your son is still feeling anxious?
Canard islanders tell Brits to go home.