I have 2 cattle dogs plus 6 shelties and have 4 entire male sheltie dogs who exercise together with my girls, now spayed. There is jealousy between two brothers who were not reared together but I give them all equal attention and have shown them that I won't put up with jealousy and fighting and they are fine. If I sit down they don't go off and play, they all want to be next to be on my lap for a love-in. Sweet dogs.
If you obedience train your dog and get a strong bond with it, being in a pack situation does not destroy that bond. I have had a bitch have a litter of 11 pups(Australian Cattle Dogs) and the day after they were born, if I left the room, she would jump out of the whelping box , leave them to follow me. Now that's devotion. Not actually what I wanted her to do, LOL , but all my dogs are like that. You need to be pack leader, especially when you have say 6 cattle dogs instead of 6 shelties, it is much easier with a pleasant little breed like shelties. I have never found either breed distancing itself though. Mine compete for my attention.