There are many members of Jessie's family, the Prescott family, that have been mentioned throughout the series. No one from the family has been shown except Jessie, but many of them are mentioned. It is also mententioned that Jessie is an only child but she mentions in One Day Wonders that she has a sister.
Jessie is the main character of the entire show, Jessie, and is the only one seen of the entire Prescott family so far. She takes after her father a lot. He taught her many things that she uses to help nanny the Ross kids. She was a straight-A student and a high school graduate (Class of 2011) in school, she has a squeaky-clean record, she's a well-rounded girl, and she loves music. She works as a nanny to the Ross kids to earn money for college.
Mr. Prescott is Jessie's father. He is part of the military. He taught Jessie a lot of things. He taught her how to survive in the desert with nothing but a toothpick and a bobby pin. He also taught her how to fly a helicopter and use an AK47. Mr. Prescott sometimes has a strange desire to make someone punch him in the stomach.
Not much is known about Mrs. Prescott but she was mentioned by Jessie in the episode, Badfellas. In G.I. Jessie, she mention that she remembers the first time gave her very first makeup kit. She also told her to follow her dreams and would have been happy she moved to New York. Jessie's father told Jessie that whenever he looked at Jessie he saw her mom. She passed away when Jessie was younger but the cause of her death is unknown.
Grandpa Prescott is Jessie's grandfather. Not much is known about him but it is revealed in Are You Cooler Than a 5th Grader? that he drives around in his pick-up truck lip synching to Katy Perry.
Aunt Ruby is Jessie's aunt. Not much is known about her but it is revealed in Are You Cooler Than a 5th Grader? that she wears a belly shirt that says, "Don't Mess With Texas" to Thanksgiving every single year.
Uncle Randy is Jessie's uncle. Not much is known about him but it is revealed in Are You Cooler Than a 5th Grader? that he has ferrets who jump rope.