I think of the nuclear family more as an invention of 20th century ad campaigns. It’s a lot harder to sell mom cooking and cleaning products when she has help from an extended family.
Many people thought this, e.g. it was assumed in Victorian England that the past looked a lot like the present of less-developed countries, like Russia.
But it's not true, we have data. The quite readable book on this is Laslett, "The World We Have Lost". https://www.telegraph.co.uk/news/obituaries/1362413/Peter-La...