"They were joking. It's a running joke because there are so many of his kids working on the show in some capacity. Bellisario usually has several of his children working on his shows. Son David Bellisario is a producer on NCIS and daughter Julie B. Watson is a coordinating producer on the show. Both are his children from his first marriage. Michael
Bellisario (second marriage) appeared as "Chip" on NCIS and in JAG and in Quantum Leap as a child. Troian Bellisario (third marriage) appeared as "Sarah McGee" on NCIS and also in the Quantum Leap episode "A Picture for Troian" when she was very young. He is currently married to Sean "McGee" Murray's mother, VIvienne and Sean's brother Chad W. Murray also works on the show in the editorial department (he was also "Russell MacDonald", the Navy seaman who chained weights to his body and tried to walk to shore to prove his immortality in the season 1 episode "The Immortals.)"

And that's as accurate as I can get, since I don't know the family personally ;) But all of that info. I have read in interviews or heard in interviews with Mr. Bellisario and on episode commentaries, etc. Sorry for the rambling. Got carried away there. I'm running on 1 1/2 hrs. of sleep and caffeine fumes today, so I'm a bit "Abby" today ;)"