Awww...

When you just have a baby, there's this tremendous social pressure to
1) Believe how cute the baby is
2) Know who the baby looks like

So you'll get comments like "Oh! How cute! So who does he look like?" or, "A baby boy? Congrats! Does he look like you or your wife?" or the more direct one such as, "Awww...look, his jaw takes up the dad. And see the resemblance with the mother!"

This doesn't apply to, say, grandparents.

"Oh, so this is your grandpa?"
"Why, yes... a little shriveled up and delirious, but still kicking nonetheless. We just got him out of jail for mistaking a policeman as a tree, and himself as a territorial dog."
"Oh, how cute! I can see the resemblance."