When he was born in August, little Sammisano weighed more than 16 pounds -- more than two times the weight of an average baby, ABC7 San Francisco reports.
At five months, he now wears clothes made for an average two-year-old.
Sammisano's family is investigating whether he could be the biggest baby ever born in the state of California.
Get more on this story from our sister station, KGO-TV in San Francisco.