Kylie Jenner and Travis Scott have welcomed their second child to the world, and .... it's a boy!!!

Kylie announced the birth of her son Sunday, saying the kid was born on Wednesday -- and indicating the baby's sex by posting a blue heart. The photo she posted to break the news features what appears to be Stormi's hand reaching out and touching her little brother.

KJ also tagged Travis in the post. No word on a name yet -- but we're sure that'll be forthcoming.

As we reported ... the Kylie pregnancy news broke in August after a few weeks of speculation and internet sleuths finding signs almost daily that she was expecting.

Not long after the cat was outta the bag ... Kylie officially announced her pregnancy herself with an emotional video documenting the early stages and featuring Travis, Stormi and Kris Jenner.

Kendall later revealed that her sister broke the big news to her the old-fashioned way ... by calling her up and showing her the sonogram.

What was interesting about Kylie's second pregnancy, is that she was a lot less private about it than her first. She got out of the house a lot more, and wasn't afraid to flaunt her baby bump in public either.

Kylie previously stated she felt pressure to have a second child and give Stormi a younger sibling, so now that she's done it ... the official Kardashian crew kids count is 11. And, Caitlyn Jenner's grandkids tally is up to 20!!!