My dad has been a Celtics fan since the days of Cousy and Russell.
All three of his boys are Celtics fans today — although the youngest of us grew up a Bulls fan and roots for the Celtics primarily because rooting for the Bulls has largely been an exercise in masochism for over twenty years now.
A few years ago, my dad started a group chat for the four of us, primarily for discussing basketball because when it comes to football, we divide our loyalties among three NFC Central teams. Last year, he added my two nephews to the chat because when they were both very young and impressionable, the Celtics dismantled the Lakers en route to their 17th championship.