stray male vs other males, opposed to a spayed female

my sister and i live about 200 yards apart in the country. she has 4 un neutered male outside cats, only one of which is petable....i have one 12 year old spayed outside female. a poor skinny stray male has been going to her porch in the middle of the night...and a fierce cat fight results...but at the same time..i have caught him here...stealing food, and the old female doesn't have a problem with it....he fights so fierce with my sisters male cats that its getting out of hand...but no fight here...so i am wondering if he is just fighting for his life and if there is anything i can do to help him, and keep him up here, and feed him without him causing such trouble at my sisters.....when i actually catch him on the porch, he runs away...i would appreciate any help or adivice...my brother in law thinks he should be put down, but after thinking about it, i kinda had a Jesus moment, and think he just needs help...please help me? thank you.l

Would your sister be amenable to doing a TNR with her males?  It doesn't do them any good not to be neutered.  If you could trap and neuter the skinny guy, he might stay in your area with your old female and be happy and not go to the other cats' territory.  If these boys are all neutered, they will learn to live in relative peace with just a little paw waving and chasing but no bloody battles.

I agree with Red Top.   TNR is usually the trick.  Or TNR with following adoption...   

Neutered they will also be easier admitted in by  territorial females, or into colonies of females.