Yes, the Music Star is the V6, the Familitchi is the V5 (and V5.5 for the Royal Familitchi.) The Music Star can connect with the Familitchis and the Tama-Go.
Yes, and they can even marry each other! Only thing is that, when the V6 wins a game against the V5 it doesn't get money, while the V5 gains 30$ when winning against a V6.