Agree with all above, neuter NOW. When my D-in-Law moved in with me with her three cats to add to my two (not to mention her extra dogs with mine ) they all kept their distance but have now accepted each other. An occasional "slap fight" with eyes closed but silly noises.. but get your younger cat "fixed" even if he doesn't think he's broken
So sorry, I forgot to say WELCOME TO PET TALK, WE ARE HERE FOR YOU AT ANY TIME