Three in the one house

Bit of a long story here.

My Father and I got a male and female as 8 years ago.

They breeded and one of the pups ( a male ) went to
my now Stepmothers house.

Dad got married, sold the family home and moved to
my Stepmothers house, with both dogs.

So there are three dogs around the house – the Father,
Son and Mother.

Ever since the move, the Father and Son cannot get on
- they growl and posture at one each other a lot ( it seems to be getting worse ). Inevitably there is a fight,which the father always comes off worse ( he has had about 15 stitches in 3 separate fights - but gave the son a ‘Van Gogh’ ear in one ).

Lat week they fought again – this time my Stepmom got
bit when she tried to separate them.

When the 2 dogs are on neutral territory, they are great - they hunt together.

Obviously, this cannot continue – it causes a lot of stress for Dad, Stepmother and my Step-Sisters /Step Brothers.

The son is the ‘Steps’ dog.

The only solution we see at the moment is to have the
Father put down – heartbreaking for all.

Has anyone come across something like this before – I’d like to know that we tried everything before making a decision ?