The father's first son follows in his footsteps taking over the financial obligations of the estate. The land of Israel is called an inheritance. Thus, as all inheritances, it would be passed from father to son. The division of land is by shevet. Land can be leased, but not sold.
Every tribe holds onto their own portion of land.
We have to picture the effects of this. Each family of Yehoshua's generation received a portion of land. This land stayed within the family until the end of Bayis Rishon, divided and redivided as the family grew. This would mean that no only do you live within your shevet, but your immediate neighbors are your extended family. Since the concepts of shevet and family are rooted in an inheritance, the tribe of the child is that of the father.