Thanks for your question. I will try to help.
My answer assumes that he did not contribute any monies to the initial purchase of the property and they will remain unmarried.
The position is that where a person is not named on the registered title to a property then you can generally only claim an interest in the property if you have made either a capital contribution to it (ie. financing the purchase or pay for significant works which materially increase the value of the property) or have maintained the mortgage payments/paid rent or bills/food to a total that is more than you would otherwise have paid in private rented accommodation in the area.
Provided he has not contributed more money than he would have otherwise paid in private rented accommodation for rent/bills/food and has not made improvements to the property which increases its market value then he would not be advised to make a claim against the property
So, on the facts as you have stated he will not be able to make a claim on the property now or upon her death.
As to his occupation if he does not have a tenancy agreement or other agreement governing his occupation then she does not have any obligation to house him permanent and he would be regarded as an excluded occupier, which means that your mother is only obligated to serve him with reasonable written notice of his eviction. The actual amount of notice is not defined, but if he has lived there for two years then 2 months’ notice would be sufficient and then if he had not left she can apply to court to have him evicted.
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