Have to pay the bills or can he refuse?

Long story short, my Brother and his ex-partner (not married), have two children together and have been living together for close to 15 years in a house they have bought together.
They split up around 3 months ago after a long drawn-out process of his ex cheating on him with both men and women (again, this is the short version of the story).
They are both named on the deeds to the property, but my Brother has been paying the mortgage ever since his eldest child was born 8 years ago, as well as all bills. She literally has not put anything into any of it.
She is currently unemployed, and claims she is trying to get a new job, but refuses to work more than 3 days a week, and will only work school hours, for 'the sake of her mental health'.

He wants to sell the house so they can have a Clean Break, they previously agreed to split the house 50/50 on sale, as well as split the kids time 50/50 between them, and he wants to rent a house somewhere afresh where the kids don't have the confusion of living with two parents who constantly argue.
She is now digging her heels in and refusing to sell the house, despite the kids suffering as a result of the constant animosity between them. He hates this and is at the point where he is willing to stop paying the bills and have the house taken off them and end up with nothing, to get away from her.

My questions are:
1) What are his options as a non-married couple with 2 kids, with an ex-partner that refuses to move or sell the house?
2) If he refuses to pay the bills and decides to rent somewhere else, would there be any legal recourse in terms of him being forced to pay the mortgage?

TIA for any replies.