What kind of sister?

In the ongoing saga of my brothers relationship breakdown I’ve found myself wondering what sort of sister am I? Do I pledge my loyality to the family relationship to the girlfriend as a woman….

My brother and the girlfriend lived around 2 miles from my parents home in a northern city, he had a good job, she had a baby, he was happy, she was miserable. Her mum lives around 250 miles away in the southwest in a little wooden house on the edge of a river….The girlfriend asks the brother to move down there and give their baby a different life. He agrees- he wants them all to be happy. They rent out their home and move next door to the mother-in-law; and conviently next door to the grandmother-in-law. My brother gets a new job- the girlfriend is still miserable. She ends the relationship and moves back to northern city leaving him heartbroken, without his baby, living in between his ex inlaws. On top of the heartbrake of the relationship ending he feels she took him 250 miles to dump him.  

She now wants her equity from the family home and arguments break out about how much this is; he desperately wants to keep the house as he feels he’s lost everything else. So as his sister I can see that she shouldn’t have the equity; legally he put the cash in and now gets the house. However as the other sort of sister I feel great sympathy for her- she was the homemaker;looked after the child and spent any money she had on food, nappies etc. So should she now lose out?

As the argument drags on it looks more likely that lawyers will be involved and the discussion is ended- they get any cash available!