There will be actual brothers and sisters again. Interesting fact, in China, cousins act as a sort of replacement for the lack of brothers and sisters during the one-child policy, prior to the policy the chinese had large families, then there was the implementation thus  you had a lot of siblings with only a single child. This generation grew up with loads of cousins, however, with the one child policy generation, there will be a generation without 1st cousins, their children however will have brothers and sisters again. The one child policy generation sounds like a lonely one without nieces and nephews.