He's wasn't their brother like destined said below but now he kinda is.

I mean Matt brainwashed him into believeing he was Nathan so in essence Sylar got his(kinda) wish and became a Petrelli.

Oh and Sylar was totally macking on Claire made me uncomfortable and ewww.

I mean I write petrellicest and him caressing her face and talking about how she could be his 'first' first lady had me going making weird, omgwherestheguyfromdateline, faces.