When you get several litters together, they soon treat each other as siblings and best of pals. It's interesting. Many many years ago when we first started we used to keep them separate in the thought that they would bond to their siblings. They were always curious but not bonded as we see today. When we started putting them together at 4 weeks or so, we saw deep relationships develop and found it was a positive thing. The more siblings one has the more you have to deal with personalities making them a more rounded puppy. Too many benefits to doing it this way but I bet you get confused as to who belongs to whom.
We're finding it too hot for the puppies so we had several play sessions today. We are only holding the early one outside. By the time it cools off, it's time for bed.
Pups have really made the leap of playing wherever we bring them. They are truly wonderful pups!