3 fights in a week and a half with other dog.

I have a Rottie female about 3 and a half and 18 mth Female Staff and 12 yr old mongrel terrier male.

They got on great and live together.But the last week and a half the staff has battered the 12 yr old male 3 times and made him bleed all 3 times.I dragged her off him everytime.But worried I may not be there someday and he could have been badly hurt as some of the cuts were near his eyes and jugular in his neck.
So now I have left the 2 girls out side and taken the old male in to live on the sofa away from other dogs.

He starts the trouble as he does be barking at noises he hears now and then.She gets in his way wanting attention and he barks at her to go away then she pins him to the ground and does not let go even if he is whimpering.

She actually gets on with cats people and other dogs and especially kids.I just think she is being very aggressive and should not be fighting that hard since she has lived with this older dog since she was 9 weeks old.And most of the time still likes him and they sleep together.Should I neuter her.Or keep them away from each other a bit.
She has never fought or had a row with Rottie who is like her mother.

Hello! Oh dear - what a tough situation to be in. Could you offer anymore background info - when you say the girls are outside do you mean they live outside all of the time? Definitely don't leave the two that are fighting together when you're not there, that could be a recipe for disaster. Are any of them crate trained? Are they ever left alone for long periods?

General questions - do you walk them together? How much exercise/socialization time do they all get? So, do you think she's reacting to him barking and attacking him? And also attacking because she feels that he's getting more attention than her?

The 3 of them live in a large kennel with pillows and a duvet and have done so all there lives.I had a Boxer female who died 2 mths ago of cancer age 11 so there was 4 of them.And never any fights.

I kept him on the sofa all night and now he has swelled up where he was cut.So he went out the back with me for a few mins and the 2 bitches ran up to him as they missed him and tried to lick him.But I am keeping him in just in case.The Staff was playing with a kitten last week and licking it like it was her pup so she is not vicious.The trouble is the male likes to have a rant now and then and thinks he is quarding the garden from the world.When she jumps around him she bumps off him and he says get away but she over reacts and bashes him.It is only when he is being aggressive and barking that she gets into a mood herself.She may be copying him now she is older and the older Boxer is gone maybe she feels she has to be top bitch now.But still never fights with Rottie bitch who is very calm always and does not even bark.

also I bring him on walks on his own always as he hates other dogs he meets and I do not want my other dogs to copy him.They are ok on walks and not aggressive He is though being a male and thinking he is great.He was always aggressive with animals and people apart from me and the family.But the staff is challenging him as top dog now it seems and winning easily.So it may be best to keep them apart.

To be honest, I wouldn't like to try and guess at advice on a situation like this. I'd suggest you contact a reputable behaviourist who can come and meet you all, and then advise you based on what they are seeing on the ground.

Good luck!