I no longer have a stallion but when I did,I rode my stallion on trails & in clinic group setting of mares & geldings
. Proper behavior/manners for stallion is something that is to be started young & is ongoing. You have to be consistent & not can't be lax on correcting them.Most learn what is acceptable behavior. I would not turn your gelding & stallion together , but working them or riding them in same arena or on the trail is good
. If you are wanting to show your boy he needs to learn what is proper behavior working around other horses. My stallion was kept separate area but could visit over fence to other horses in one small section of fence of his one field (He respected his hot wire). My young stallion I also let live with the Preggo broodmares in winter they taught him alot
I think these things did help his socialization with other horses.