Machir was the only son of Manasseh (Genesis 50:23; Numbers 26:29). His descendants were the half-tribe of Manasseh who already received a separate portion east of the Jordan in Gilead and Bashan (Joshua 13:29–31). The rest of Manasseh’s portion was west of the Jordan (Joshua 17:2, Joshua 17:7–11). All the clans listed in Joshua 17:2 were descended from Gilead, so it is not clear if there were other sons of Manasseh who received the land in the east and if these sons received land in the west.1
1 Then allotment was made to the people of Manasseh, for he was the firstborn of Joseph. To Machir the firstborn of Manasseh, the father of Gilead, were allotted Gilead and Bashan, because he was a man of war.