I think you have every right to ignore these people. You don't owe them your online connection. It says a lot about the son of the family friend if he is being so sensitive about not being your online friend.

When this happens to me, I block people. I've worked too hard for my sanity and emotional wellness to let toxic people in.

Do what is best for you. Block them. They are adults and they need to act like adults. They are not your problem.