Ellis Grey- Meredith's mom who cheated on her dad with her co-worker Richard Weber, who is now Seattle Grace Hospital's cheif and Meredith's boss; Ellis had Alzheimers and Richard went to check on her without Merediths knowledge (she is now deceased)
Thatcher Grey- Merediths dad who left her and her mom and remarried and had other kids; when his new wife died under Merediths care, he started to drink and get violent