Genesis 36

This chapter is a detailed epic catalog. The text strongly suggests Aholibamah and Eliphaz in 36:16 and 36:18 share a child, Korah. Aholibamah is Esau's wife, and Eliphaz is Esau's son.
Korah is listed as a descendent of Eliphaz, 36:16, a 'son' of Adah (Esau's other wife) in 36:16, and a 'son' of Aholibamah in 36:18.
There is no way a child could be considered a son of both women's lineages unless a child of one of the women was the father. Grandchildren of a woman was considered her 'sons,' or souls that came from that woman.