Without love, babies fail to thrive and they literally can die.
I've never heard of this. There are a LOT of babies who manage to grow up in horrific conditions, certainly not in any king of loving family as most people would recognize it. I don't say they would grow up mentally healthy, again as we understand it, but they do survive.
It happens in some very poor orphanages. I'm thinking more of a society level than an individual level for those other examples.