The Conners producers weighed in on the possibility of Johnny Galecki and Michael Fishman reprising their original roles again. They originated characters on Roseanne, the sitcom which the new show directly follows, with Fishman playing eldest son D.J. Conner from episode 2 of Roseanne through season 4 of the sequel and Galecki playing David Healy, with whom D.J.’s older sister Darlene (Sara Gilbert) has a tumultuous relationship, across 98 episodes beginning in Roseanne season 4. The Conners season 7 will be the final season of the show and neither star has so far been confirmed to appear.
https://screenrant.com/the-conners-johnny-galecki-michael-fishman-returns-update/