My partner has lived in his house for 15 years, his ex and himself are both named on the mortgage.

They have never been married but have 2 children aged 22 and 17 still living in the house with there mother.

My partner now rents but still pays all the bills to his house, his ex partner never worked and never contributed financially or otherwise to the house. She now has a job and has been working for the past year, but she still doesn't contribute financially or otherwise.

Is she entitled to half the house?

Whose name is the deed in? Are they in a community property state?

What names are on the mortgage do not necessarily prove ownership.

Since they have not been married and if he can prove he has made all the payments towards the mortgage, unless her name is on the deed, then she doesn't have much of a claim. But if she is on the deed then the house is half hers.

Yes, it is whose name is on the deed. If both names are on the deed, they both own the house and how the names are listed makes a difference.

But if they are, it is very likely she owns 1/2 and he will have to buy her out, or she him.