Parents are soap opera-actress Lesley Vogel; and Alan L. Skip Panettiere, a fire department lieutenant.
Like his actress-sister Hayden Panettiere, Jansen has a fondness for music and gymnastics as well as acting; he plays guitar, and can do a mean standing back-flip.
His last name is pronounced "Pan-Uh-Tee-Air-Ee"; the Italian translation is "Baker". His father has Italian ancestry, and his mother has English and German ancestry on one side and Italian ancestry on the other (Jansen's maternal grandmother's parents were Italian immigrants).
Younger brother of Hayden Panettiere, with whom he shares great affection and loyalty. They starred together in Tiger Cruise (2004).