The descendants of Zebulun

In Numbers, chapter 26:26-27, the three descendants of Zebulun all have the same name and spelling as in Genesis.  Esau married the daughter of a Hittite man named Elon.  Otherwise, there was no mention of these three guys anywhere else.  Sered had his clan of the Seredites.  Elon has his clan of the Elonites.  Jahleel had his clan of the Jahleelites.  The descendants of Zebulun also increased by 3,100 from 57,400 in the first census to 60,500 in this census.  What do you know about Zebulun?