Sebastian

 Sebastian is a Smosh character who appears in few Smosh videos. He is portrayed by Anthony. It is possible that Fabio (Ian) is his boyfriend.

IF APPS WERE REAL
Sebastian is featured in two apps in the sketch. In Grindr, where Fabian asks him if he wants to grind with him. He agrees as they start grinding raw meat into sausages.

He also appears in Google Maps app, where Sebastian, along with Fabian, asks Ian and Anthony if they want to grind some meat with them.