Would a child be healthier if it was raised by more than 2 people?

Those children raised in families with close ties to grandparents/aunts/uncles etc seem to have some social benefit. Which could mean opening potentials in them and indirectly opening opportunities too.

Yes, optimum child raising number is 16.

All a child needs is love, and it depends on the two parents.
A child can be raised with role models ( friends, family) from a single parent, much better than two abusive parents.
But will just come back to all a child needs is love

I sometimes think it takes a society to raise a child - good parents/family, school, government

There is a saying, although it isn't practiced anymore in North America, that goes:

"It takes a village to raise a child."

So yes, a solid family unit + community support (extended family/trusted confidantes) makes a huge difference.

The only way I can see this being a problem is creating the personality