I believe the correct answer is: Mosuo.
The Mosuo (called the Na among themselves) are a small ethnic group living in Yunnan and Sichuan Provinces in China, who trace their lineage through the female side of the family and occasionally may even not know who the father was.
Mosuo people are practicing "parallel line of descent" in which the father passes his social status to his sons, while mother passes her status to their daughters (matrilineal descent of title and property).
They are also practicing the “walking marriages” which means that there is no formal marriage (they do not technically live in the same household, but men are free to visit when granted permission) and the children stay with their mother.