It was revealed previously that the two would be making an appearance, but we now know just who will play them.
Alicia Coppola (picture far-left), who began her career in 1989 as a host of MTV's "REMOTE CONTROL" game show has been cast as Derek's mom, Talia and newcomer Ana Walczak (picture far-right) has been cast as Derek's sister, Laura, respectively.
This recent announcement follows Ian Nelson being cast as Young Derek.
Read more spoilers on the very episode they'll be appearing in here!
Do you look forward to exploring Derek's long-forgotten family tree? And will they bring Derek happiness or anger him even further?