“Whatever made me think that a guy like me should have a daughter... I never deserved her. Not for one second.”— Kellogg's commentary
Mary was the daughter of Conrad Kellogg and Sarah. Mary died sometime before 2287 but how and when exactly is unknown. Some information about this is disclosed during Shattered, when an unknown person speaking to Kellogg is saying "they died like dogs... and you weren't there to protect them."