Quote Axl Rose: I don't know why I didn't think of this before but could Fluke really be Damian Smith back from the dead and Damian had plastic surgery to make himself look like Luke? Think about it
He was the son of Frank Smith, he hated Luke.
He had dealings with ELQ.
He was a womanizer. Was sleeping with Lucy and Bobbie.
He was with the mob. I can see him wanting to take Sonny down because he took over the Frank Smith dealings.
and another thing that matches maybe is the spoiler/rumor that Ned thinks Fluke reminds him of someone and Ned and Damian were at boarding school together.
So Luke could very well be Damian Smith and if that is the case then I could see Damian working with Julian to take down Sonny considering Sonny took over Damian's father Frank's territory