Older son had 2 kids...one was the hyuga clan ancestors and the other the uchiha's
The younger son had 2 kids one became the senju and the other became the uzumaki.
With the elder son he had a dojutsu that was similar to the rinnegan, not a sharingan. So maybe sharingan+byakugan=elder sons dojutsu.
the younger son inherited the so6p body, and physical powers...that means that is life force jutsu and physical stregnth(chakra)
the uzumaki are well known for their life force, and sealing jutsu....while the senju are well known as being jutsu masters and haveing large amounts of chakra
so simply here is what i think of their percentage of being desendents of so6p....uzumaki and hyuuga are 1/3 of younger and elder son bloodline(or 1/6 of so6p) and the uchiha and senju are 2/3 of elder and younger sons(or 2/6 so6p power)
i am going with the assumption that the succesors of the elder and younger began useing the strongest to be leader of what became the senju and the uchiha clans...(so basically senju and uchiha are based on being the purest branchs of the sons