If you really mean "ancestors" rather than "descendents", my best guess would be the Peruvian pre-colombian peoples. In their worldview, there were three worlds: Hanan Pacha (heaven), Kay Pacha (our world, which "mother Earth" or "Pachamama" is a part of), and Uku Pacha (the underworld). The dead interacted with the living in many ways, mainly related to fertility, such as fertilizing the soil for agriculture and being the craddle of new generations. For these reasons, they cared deeply about preparing the passing of deceased leaders and maintaining values and rituals (e.g., sacrifices) to keep their ancestors happy. 

Another guess would be the ancient Egyptians, who also had elaborate rituals for the dead and deities associated with the deceased. I don't know much more about them, though.

Do you mean their descendants?