Yeah we have Penny and Theo (The little dogs) and they have sibling rivalry, if one is getting cuddled the other pushes in and has to get cuddled aswell. They are great friends though and love to snuggle together.

Clover and Elvis are actually great with one another and will take it in turns with affection and training.

A friend of mine has a real big problem with two of their Labs, both males one intact the other neutered they cannot be near one another and try to kill one another all because they want to be #1 with their Mum. The yellow lab smashed through a window to get to the black labby and both got pretty badly cut up.