What makes someone "naturally" good with children?

The person could do nothing particular -- yet the child automatically loves them! It just baffles me!

Recently, I visited my friend's one-year-old nephew. From what I've been told, he's extremely shy of anyone besides his family-- even children his own age! But when I first walked in that door and saw him, he didn't run away. He initially just stared and smiled. He waddled to me, I extended my hands, and he hugged + high fived me. His whole family and I were mindblown lol. They then applauded me for being the first person that he approached at his own will ever!

What makes children be so comfortable with someone within a few seconds?
What makes someone "naturally" good with children?
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