AIO about a statement a Catholic Saint made towards my fiancee and her little sister at Thanksgiving??

Long story cut very short, Fiancee (21F) and I (23M) went to Thanksgiving with fiancee's VERY Catholic mother. Her mom and dad don't like each other, so it's just mom, her siblings, and us.... Then some random priests from their church that her mom invited. They are very sweet people from Africa, and I don't mind them, except for one specific Saint.

At one point, it was myself, fiancee, fiancee's little sister (18F), and random Saint. We were chatting and whatnot, and then after a lull of conversation, he comes with the question of when we are going to have kids. I answer kindly, we don't mind that question at all. Then he asks her little sister, who says very truthfully how she just wants to get through college first.

Saint whatshisname then comes out swinging with "You two would have BIG bumps if you lived back home!" With a few little extra comments about how ripe their ages are and how beautiful they are. After I was done picking my jaw up off the floor, I tried my absolute best to bite my tongue and tell him I'd like to switch topics, as my fiancee and her sis were looking at each other like they just watched someone jump off a bridge.

Fast forward to an hour ago of this post, and my mother started crying to my fiancee about how she's not a REAL Catholic (she doesn't want to be, but didn't want to break her mum's heart) and even began laughing off that very off-kilter comment. I had half a mind to pop dude in his gums. Am I overreacting to this comment?? Thank you, hope you all had a blessed holiday!