The 22-year-old Larson, the 2014 Sprint Cup Rookie of the Year, tweeted about the birth early Tuesday morning:
Sweet is the sister of Brad Sweet, a sprint-car racer who also has competed in NASCAR.
Larson finished 17th in the Cup standings, the highest a non-Chase driver could finish. He had eight top-fives and 17 top-10s in 2014.
