The apple ain't fall too far from the tree with Cristiano Ronaldo and his 13-year-old son, CR Jr. ... 'cause the two look just alike -- even down to their shredded abs!
The proof's in the photos that 39-year-old Ronaldo dropped Thursday on Instagram featuring Cristiano Jr. ... giving his 622+ million followers a view of their physique during their workout sesh.
"Today with my partner u2764ufe0f," Ronaldo said in the caption.
The father-and-son snap got over 9 million likes within five hours .