I see no reason why Lucas would want to live with Sidwell ... or why Marco would want him to, especially since Marcus lied to Alexis and is involved in his father's business.
Having Lucas in the middle of the Sidwell household is dangerous -- didn't Lucas used to be a police officer -- is he planning on rejoining the force, if not what job will he do?
Either way, if Marco loves Luas, he wouldn't want him anywhere near his father's criminal empire. Not to mention as an adult couple, moving in with his dad makes no sense.
Karen L.