Do grimers hatch from eggs?

I hatched 1 yday from 5km all my eggs after after the update so yes they still hatch. They come from the randomnest stops like Porygon and Mareep. Keep trying! Don't settle for that Muk lol!

Yes they do, but before gen 2 and eggs changes from valentines he was harder to hatch than porygon, I think he probably still harder.

I've hatched 683 eggs (not sure how many 5km).

Got 2 Porygons and 1 Grimer in gen1.
Got 1 Porygon and 2 Grimers in gen2.

They seem to be the rarest hatchs from 5km eggs.

Yes, they do!! I've completed my muk only with grimers hatched from eggs, needed 3 of them

It could be very good the only Pokemon from Gen1 I never managed to hatch.

I have only seen 1 Grimmer and it was the one I hatched back in July 15, 2016 and thank god it has good ivs because other wise i'd still be waiting for a good one to evolve it into muk and thank god for the halloween event since it made it easier to get candies for it as my buddy pokemon. (side note ive hatched 358 eggs as of now). I also find grimmer and koffing to be another rare hatch since ive never hatched one at all and ive only ever caught 7 randomly and walked a bit with it to get it up to 50 candies whenever I do hatch or catch a good one.
UPDATE: I hatched my second grimer today

I've hatched 1,687 eggs and I would estimate 5-6 have been grimer. If anything I may be underestimating. I just hatched one about a week or so ago.