So what, if anything, did you say? 

My knee-jerk reaction would have been along the lines of “Oh yeah? I really don’t give a f***, but thanks for sharing.”

I mean, seriously. Did they stop by unannounced just to drop that information in-person to see your facial reactions? Because it sounds like it. Like they were biting at the bit. They sound like a couple gossiping busybodies. Blech.

Personally, it was a glorious day when I stumbled upon the fact, via social media, that BM was pregnant with her 2nd child, therefore HAD to be getting married before the baby arrived. Which she did. Just like she did with DH. LOL.

And I wouldn’t have been bothered much that they decided to just stop by, being “in the neighborhood,” and all (which I feel is a BS story), opposed to the words that were coming out of FIL’s mouth upon entering the kitchen in MY OWN house. 

It’s so silly that it’s laughable. I hope this has you laughing for days, OP, because it would me. So much so that my DH would be feeling secondhand embarrassment from his dad’s behavior. 

Yep, they sound like gossiping aholes, and the way he worded it "your husband's ex wife"....that part just seems like him trying to add more fuel to the fire too!  I like that he had to actually say "BM, she got married" before you figured out wth he was talking about.....

In every conversation, my MIL finds some way to talk about BM and her life, as if I care.

I’ve told MIL multiple times how BM harassed both DH and me and MIL still seems to think that DH just isn’t working hard enough to “work out his differences” with BM.

Also, BIL falls all over himself to reply to any email from BM but ignores me even when I ask him what his kids want for Christmas.

That and Silent SiL talks to BM even though she’s talked to me once. (According to DH, BM and Silent SiL we’re not besties when they were married).

In-laws suck. If I had to do it all over again, I never would have married someone whose family had not moved on from his divorce. I wouldn’t marry someone whose family made me prove to them that I was worthy before they would consider me part of the family. My family is so welcoming that it honestly never occurred to me that someone else’s family could be so sh$tty.

Your FIL is my MIL.  I keep MIL at more than arm's length.  She's not my type of people. 

(And she raised two boys with a certain amount of brokenness that's led them to 3 divorces between them before the oldest reached 35).

MILs never met a boundary she didn't happily stomp.  Seems neither has BM.  That they couldn't get along during the marriage is no surprise.  That they've teamed up afterwards is a bit odd but true to character.  No skin off my nose.

MIL would thoroughly enjoy parading BMs remarriage.  Only problem is that BM hasn't and doesn't appear to be moving on any time soon.  Unfortunately for MIL that opportunity may not come in her lifetime.  Aww.

I suppose I'm mean spirited enough to find it amusingly pitiful but I do find it all comedic.  I also try to dig deep for some empathy once in a while, though.

I mean how sad is your life to be unable to move on from the past? To force yourself to survive on unrequited love or a deranged one sided competition?  To sacrifice every great thing your future could be so you can play the martyred victim forevermore?  

And how messed up are you to be a third wheel flying monkey - if only on rare occasion - to find some perverse enjoyment in trying to stage another competition, more conflict, with what you think are old wounds others must have because YOU haven't moved on?

Sad, sad little people.  So insignificant in their own lives to wreak havoc for a sliver of a chance at being relevant to somebody somewhere.

Your FIL is a punk.  Try to recognize him for the broken unfortunate human being he is.  His need for conflict and negativity is not a reflection on you but should tell you everything you need to know about the person he is (and likely always has been and always will be).