Staci Keanan and Christopher Castile had previously appeared on the Miller-Boyett-produced ABC sitcom "Going Places", which debuted the season prior to "Step By Step", playing characters with no familial relation (Keanan – who played Lindsay Bowen, the teenage neighbor of the show's adult characters – as a series regular, Castile as a recurring character). Keanan was the first of the two "Going Places" stars to be cast on "Step By Step" in the spring of 1991. Castile, who had played gawky child Sam Roberts on "Going Places", brought the same character traits to the Mark Foster role, which was speculated to be Miller-Boyett's continued attempt to give the "Family Matters" character Steve Urkel a white counterpart. In a similar instance of hiring actors over from their other TV series, the producers also cast Josh Byrne as Brendan Lambert on "Step By Step", after he had just finished a supporting role as Patrick Kozak on Miller-Boyett's single-season CBS sitcom "The Family Man".