The musical power couple -- who just welcomed their latest son, Riot Rose, in August -- posed for some incredible shots at home ... with both the new 1-month-old baby, and their other kiddo, RZA.

We gotta say, the Mayers look super happy and gotta be one of the best-looking crews in all of Hollywood.

Mama and Papa Bear definitely took a similar fashion theme. RiRi is sporting a royal-blue look -- with the denim button-down -- and dad's got a pair of jeans on ... with a splashy green flannel to bring it all together.

Young RZA was also wearing jeans, BTW ... his whole getup is honestly freaking adorable.

As for Riot ... let's just say he's giving his big bro a run for his money in the cuteness department. The proud parents had him swaddled up in a blanket -- but underneath, the baby was decked out in a salmon-colored onesie.

Also worth noting, this is the first time we're seeing Rihanna since she popped. It probably goes without saying -- but she's looking damn good.