One of our cats came from a household where she was very neglected and a toddler used to "play with her" and pulled her hair out and such.
She was very wary of our newborn (understandable). Our baby is 10 days old now and has gotten a little greasy hair, butnwe can't bathe him because his belly button has a little inflammation, so we're careful. Today, our cat started to groom his hair out of nowhere. She just walked up to the baby and started licking the more greasy looking strands. So sweet!
Like "I'm terrified of you, but we can't have you walking around like that"