
Some years ago, when I only had 3 bitches, I took two of them with me when I went to stay with Mother and her (entire) male, and left husband at home with bitch-in-season....when we got home a few days later the stay-at-home had become very territorial and had to be gated away from the others for a day before she would mix safely with them (hormones and all that I suppose) then she was back in her place.
With the ones I have now, the two males jostle for position in the pack...they are very close, but if one gets taken out without the other, to a show, or the vet, there's a certain amount of posturing when they meet again. This is one reason why I won't use boarding kennels - nowhere has room for 4 dals in together, and I don't want them separated for this very reason.