A Question about Merry

[Beatrice]

Yeah, Kalimac. That's probably the only reason Merry would hang out with poor ol' Fatty. So he could get to know his sister. (Poor Fatty!)

LOL! Anyhoo... but how could he have a son if in the family tree it didn't say that he had any kids whatsoever? And on all the major lotr sites I've ever been on, when I look at Merry's bio it says that he had no kids! Explain, please?