The Incas lived in an exogamous clan system with only two clans, Hanan and Hurin, they produced only two dynasties the first one was Hurin and the second Hanan.
so you have Hurin kings and to what we know father and son,
The founder Manco Cápac, Sinchi Roca, Lloque Yupanqui, Mayta Cápac, Cápac Yupanqui
Cápac Yupanqui wanted one of his son a Hurin to succeed him, but the Hainan rebelled after his death and put in the throne Inca Roca so the Hainan dynasty starts.
Inca Roca, Yawar Waqaq, Viracocha, Pachacuti Inca Yupanqui, Túpac Inca Yupanqui, Huayna Capac, Atahualpa
in Atahualpa times, come the conquest and the New Inca State would continue with Manco Inca.
It must be said that this is what is more accepted to historians, not what is completely true, but it is fairly robust, probably the Maya and Aztec Kings were the only ones we know, better,
although they were north and central americans, not south.
Inca Roca was the son of a second wife which was a Hanan, he was not the heir after the Hanan rebelled and killed Inca Roca half brother, he became the king
it must be said that Hanan and Hurin were the division of Cuzco society,
with Inca Roca the Sapa Inca power base came from the Hanan that doesn't mean they come from a different family, he still was the son of the old king, all members of the royal family had Hanan and Hurin blood
after they became an empire, they also had Aymara, Chimú.
but the new dynasty had his power base the support of Hanan, Roca would even change the palace to the Hurin area of Cuzco, to signal then that they were a conquered people now.
Pre-columbian monarchical rules were different of old world ones.