In episode "we need to talk" pearl and rose fuse into rainbow Quartz. Greg is Steven's dad. Greg is shocked about this,pearl tells Greg he is just a phase and he CAN'T fuse with rose. Pearl said fusion is a bond between gems Greg said "has a human ever tried to fuse with a gem" pearl doesn't know. Greg invites rose to dance so he can fuse with her but it DOESN'T work so Greg is shocked and sad. Rose is confused about why he is shocked and sad so Greg tells her why. So rose said you can't fuse with me that makes Greg sad so they are both confused so the talk about their relationship and continue dancing. Steven is half human and half gem in the episode "alone together" Steven fuses with Connie and make stevonnie. The gems think since Steven is half human he can fuse with humans. To be honest I think since Greg "mated" with rose to make Steven. In a way that is like a fusion because Steven has Greg and rose's DNA. In a fusion they both have the gems DNA.
