Cress Williams recently played a police detective named Nathan Woods from Chicago on several episodes of 'Veronica Mars'.
Back in 2000, he was also playing Officer Reggie Moore on 'ER', which takes place in Chicago.
They could be identical cousins, which of course has an established .precedent in Toobworld.
They could also be half-brothers, with either the same father or the same mother, and that would account for the change in surnames. But that seems like such a cliched, and maybe even non-PC, supposition.
And I'd much rather use the splainin that sets Toobworld truly apart from the Real World.