Steph Curry's Daughter -- Welcomes Baby Sister With A Kiss (PHOTO)

Steph Curry won the MVP, his team won the championship -- an AMAZING year, but still not the best in his family ... 'cause his daughter Riley continues to steal America's heart.

After quoting Big Sean, dancing the "Nae Nae" ... and pissing off grumpy beat writers during the NBA playoffs... Riley welcomed her new baby sister, Ryan, with a big kiss -- and the photo will have her grabbing the spotlight again.

Thanks to our friends at BSO for calling out the adorable pic of Riley and Ryan that Steph posted on IG.

As we previously reported, Riley has big time talent agencies interested in reppin' her. Safe to say Ryan will follow in big sister's footsteps.