Is the nuclear family an universal institution?

Is the nuclear family a universal instituition?

Some functionlists such as Murdock say that the Nuclear family is such an important social instititon playing vital functions in maintiaing society, that it is found in some form in every society. In other words, Murdock is saying that the nuclear family is a universal institution. 

However these example below suggest otherwise.

Nayar - This was found in the south-west india before the 19th Century. There was no nuclear family back then. A women could have sexual relations with any man she wished for, with a maximum of 12 men. This meant that when the woman got pregnant, the biological farther of the child was unknown. This would mean that the brother of the pregnant woman who was pregnant, would need to look after the child and the mother of the child. It was his responisbilty. The Nayar had no direct link between having sexual relations, child-bearing, child-rearing and cohabitation.

Communes - This devolped in Western Europe, Britian and the US in the 1960s. These people wanted to devolp and alternative way of living. They focused more on collective living rather than individual family units. Adults and children…