The father of a father is a grandfather, a grandfather's father is a great-grandfather, a great-grandfather's father is a great-great-grandfather, but no word has been decided upon for the generations before great-great-grandfather.
Baba yake baba ni babu, babu yake baba ni babu-mkuu, baba ya babu-mkuu ni babu mkuu-mkuu, lakini hakuna neno ambalo limeamuliwa kwa vizazi kabla ya babu mkuu-mkuu.