What does the sixfold relations of their lineage mean?

Question: In the prayer for the deceased,

“By this merit, may the souls of the ancestors of the …………. family and of all the sixfold relations of their lineage be free from sufferings and obtain the pleasure of peace. May they wake up from delusion and attain enlightenment. May they escape from life and death at once and attain the Great Bodhi.

And also, may all sentient beings, the myriad souls of the Dharma realm, benefit equally. Namu Myoho renge kyo.”,

what does the “sixfold relations of their lineage” mean?

Answer: Father, mother, wife, children, older and younger siblings.