The Bodhisatta was once a son, nephew, and grandson of the same exact man in one thousand five hundred successive lives (five hundred lives for each relation) and then born in the same three relationships in another one thousand five hundred lives (again, five hundred lives each) to one specific woman.
In the Lifetime of the Buddha
One time while the Buddha was traveling, a stranger threw himself at his feet and called him “son,” lamenting as to why the Buddha had not come to see them for such a long time. This man insisted the Buddha should come to his house to see his “mother” who likewise fell at his feet and criticized him for being away so long. After the Buddha accepted their hospitality and gave a sermon about old age, he left.
His disciples who were traveling with him at the time wondered why this family did not know who the Buddha’s real parents were and why the Buddha did not comment about it. So to end their confusion, the Buddha told them this story explaining his relation to the man and woman in their earlier births.