He originally had four brothers. 18 days after we got them we lost one through a surprise illness. About a month ago it was time for two of them to go to a new home, where they settled in well and are very happy.
It didn't affect him until a couple of days ago when his remaining brother got a mild fever and had to go to the clinic for the day. He found himself alone with the two older cats and all of his brothers gone.
His one remaining brother recovered quickly and was home the same day, but Gandalf has remained super affectionate and often does both the "affection" rub and the "possession" rub even well after Fluffy came back. Like he saying "My people, my home, I want to stay!"
Well he of course IS staying, and he'll chill out eventually.