Rob Kardashian: Blac Chyna's Having My Baby ... Trolls His Sisters, Hard

Rob Kardashian just kicked a social media hornet nest by joking (we think) about knocking up Blac Chyna, while also taking a jab at his sisters ... in one brilliant meme.

Rob posted the pic of BC carrying a baby car seat and saying she's out to birth the "next generation of the Kardashian name!"

It's a hardcore troll of Kim, Kourtney, Khloe and Blac Chyna's nemesis, Kylie -- especially since we know Rob's friends and family aren't happy about his hook-up with Chyna.

Funny to us ... but not so much for the sisters, we're betting.