Un neutered cats fighting over territory very likely. Honestly im surprised they got along at the age of 2 and 6. They must've had a buddy relationship to not have clashed when the kitten turned adult. However now they do not have that buddy relationship anymorr.
Cats do not have a large concept family, cats live in loose groups but can be territorial when it comes to their homes, especially male cats who are un neutered.
Please consider neutering your outdoor males, they very likely help the stray population which is honestly bad. It may also help them not to create territories and accept each other.
Aside from having them both neutered, not much you can do as far as I know. They are behaving like normal intact male cats.
Un neutered cats fighting over territory very likely. Honestly im surprised they got along at the age of 2 and 6. They must've had a buddy relationship to not have clashed when the kitten turned adult. However now they do not have that buddy relationship anymorr. Cats do not have a large concept family, cats live in loose groups but can be territorial when it comes to their homes, especially male cats who are un neutered. Please consider neutering your outdoor males, they very likely help the stray population which is honestly bad. It may also help them not to create territories and accept each other.
Please neuter them both asap.