This afternoon, Reynolds weighed in on the announcement with a pretty meta tweet.
Casting for the part was highly competitive, with everyone from Michael Shannon to "Stranger Things" star David Harbour to Brad Pitt mentioned as contenders. Production is projected to start in June in Vancouver, with David Leitch ("John Wick") at the helm.
This will be Brolin's second big (literally) role in the Marvel Cinematic Universe -- he's also playing the big bad, Thanos, in "Avengers: Infinity Wars."
Quick refresher in case you need it: In the comics, Cable is the son of X-Men's Scott Summers (Cyclops) and Jean Grey's clone (it's complicated). He has a bit of a messianic streak (he once tried to use his psionic powers to force the people of Earth to live in peace), and it will be interesting to see how he interacts with irreverent anti-hero Deadpool in the film.
In March, Reynolds announced thatin the sequel. No word yet on who the trio will attack with barbs in the follow-up film, but honestly, we're pretty sure we're still going to see it.
Updated, 3:45 p.m. PT: Adds Reynolds' tweet.