Miss Parker's family tree is complicated. She grew up believing her mother and father were Catherine and Mr. Parker. She discovers in Inner Sense that her mother didn't die when she thought and had another child named Ethan who's biological father is Major Charles giving her a common sibling with Jarod. In the episode Bloodlines, Miss Parker finds out either Mr. Lyle or Angelo is her twin brother. It isn't until Crazy when she discovers it is Lyle.

Later, Mr. Parker marries Brigitte who ends up pregnant and has the baby in the episode Til Death Do Us Part baby Parker is born. This gives Miss Parker another half sibling or so she believes until Island of the Haunted when she discovers Mr. Parker isn't her biological father but instead Mr. Raines who is actually Abel Parker, Mr. Parker's brother who was given away when he was born because of his health weaknesses.

Sydney has an identical twin brother who also worked with the Centre but when Jacob realized what the Centre was doing he wanted to leave their employ. Mr. Raines orchestrated an accident which left Jacob comatosed.

Michelle Lucca had worked for The Centre as a clinical psychologist, and had been assigned to help Sydney with The Pretender Project until 1974 when she suddenly vanished without a trace.

In March 1998, Sydney goes looking for Michelle and discovers a birth certificate for a boy named Nicholas. Michelle is listed on the birth certificate as the mother but there is no father listed.

Michelle later explains that when she found out she was pregnant she went to tell Sydney but was met with a man she'd never met who blackmailed her into leaving The Centre.

Little is known about Mr. Broots' origins or how he came to work for The Centre. Debbie Broots is Broots’ daughter. Broots won custody of her, after Jarod revealed to the judge overseeing the custody trial that Broots’ ex-wife had been using the child support Broots sent her to go on a gambling binge in Las Vegas.