What a cutie!
I do not see that he needs to loose weight, I love to see a chubby horse these days please keep him so - you've done great! He looks well loved and cared for, not fat :) He will tone more with riding and his buddy.
Conformational I also don't see anything terrible that jumps out, to me he appears to have a pretty good rear end however he does look like he stand under himself a bit, nice high neck set, well muscled (Not saggy) top line. His throat latch is a bit thick and I think his face could be more defined/larger eyes but hes a cutie.