I am not the expert on this subject, but I can tell you what I did. i had Sasha and Harley (bro & sis). They were 1 1/2when my bf and I decided to adopt Princess who was 1. We took harley and sasha to where princess was at and they met. We sat there for over two hours while the dogs played, layed down, and ate together. They had no issues. We decided we would take princess and we all rode in the truck together. Lucky for us we never had any issues. My sasha is just the most easy going dog and she let princess move right in. The only thing i felt bad was when the dogs would chase and play harley and prin would gang up on sasha. But they lived together in harmony. I did make sure that she got her own food bowl and where it was. The other two had already designated bowls for themselves. I hope it all works out for you, and I can't wait to see pics!!!