Darkstar (Zac 10)

History
Darkstar or Michael Morningstar appeared in Ben 10 alien force, Ben 10 ultimate alien and and Zac 10 Master of the Ultimatrix.

Gwen
Darkstar has a big obsession over Gwen after his Mutation of Ultimate Darkstar. One time When he was fighting Zac he said "Where's my Girl.

Kevin Ethan Levin
Darkstar dosen't like Kevin Being around Gwen after his third mutation. In some of the episodes he said that he would threartin him for being around Gwen

Megatron
Even though Megatron is a Decepticon Darkstar Trusts Megatron about everthing he says he even calls Megatron Master.