Registering the 7 y/o

I just purchased a lovely 7 year old Selle Francais gelding by Kapitol D’Argonne out of a Landor S mare. His dam was imported with him in utero and he was never registered (unsure why). Is it possible to register him at this age? Is there a point? He’s not a flip, I plan to keep him awhile, but I will probably end up selling him down the line at some point. I’m told he’s bred quite well, though I’m not well versed enough to know.

Thoughts on registering him? If yes, how?

And if you have any feedback on his breeding, let me know- I love learning all I can about my horses!