This is pretty weird.
My big male rottweiler got my female rottweiler pregnant (she is now dead, RIP Roxie!) and they had a liter of puppies (about a year ago), and we got rid of all of them except for the runt.
I thought he was going to grow up to be a small little rottweiler, but now, he's about 11 months old (his father is like 2 and a half years), and he's quickly catching up to his father's size, he's already taller, he just needs to gain a bit of weight and get broader in his chest and back and legs.
That's pretty cool that the runt of the liter is almost bigger than his father (the father's name is Barron, he weighs about 112 pounds, the son, Rocko, weighs about 103.)
I'm hoping he'll grow to be bigger than Barron. That would be cool, because Barron is the sweetest dog in the world to any human (even strangers), but he's always beating up on my big German Shepherd "Dirk", who has severe arthritis and joint problems, which they said happened because he got to big, he's very tall, but didn't develop correctly so he's very narrow. He's currently the Alpha male in the pack, but Barron is always trying to start shit with him.
And I think if Rocko got to be bigger, he might be able to knock Barron down a few pegs. Which would be good. Rocko's very sweet to Dirk btw.