Yeah but babies drool a lot on their own and if you're the average medieval farmer/farmwife you've got enough shit to do that you don't have time to monitor infant facial expressions.
Anyways, what
@GargoyleGorl said gave me a thought about how often Russ seems specifically jealous of kids, including and especially sick kids. You have him getting jealous of the bombing victims, getting jealous of the girls with their STUPID PAPER CRANES FOR TAYLOR'S FAT, PIG FACED MOM THAT AREN'T AS GOOD AN EFFORT AS A SONG, then his long rant in response to the girl who had all of those horrible burns all over her body.
I've seen him devote way more time an energy to kids who get pop star attention than any of the actual boyfriends of these pop stars. At most he got angry about Joe Alwyn, and even then he mostly ranted about Swift being shallow. But he brought up the paper crane thing constantly and the story about the burn girl getting a visit from Swift prompted a long ass rant about "the Hell he has been through." Kids seem to really be a berserk button for him.
I am trying to figure out why. But I can tell you that if Russ HAD somehow managed to get himself a young wife and family, he'd definitely be the type of shithead to be jealous of his own kids.