Question. Is having a nuclear family something humans are evolved to do. Is it a complete social construct that is unnatural to us or is it very natural to have this kind of social unit?

If not what is the most natural social unit to have?

We all know the nuclear family is in decline. It will be a slow death but steady. It's happening in Asia and spreading to western culture. But is it natural what are the new social units emerging and are they more inline with our natural instincts?

Thanks