Baby Future is not a baby anymore -- and Russell Wilson just sent his stepson a heartfelt message on his 8th birthday ... calling him the "greatest blessing in the world."
Russ was spreading love to the lil' man bright and early on Thursday -- posting a side-by-side pic of the two on social media ... expressing what Ciara's child with rapper Futuremeans to him.
"Happy Bday Future!" Russ said on Twitter. "8yrs old! You are the greatest blessing in the world to me!"
"So full of the fruit of the Spirit of Jesus!