Can beneficiary’s partner live in house owned by trust?

Trust has this clause:

“Trustees shall have the following powers in addition to their powers under general law:
to permit the property in the estate to be used as a residence by any person or persons having an interest or prospective interest in my Residuary Estate upon such terms and conditions from time to time as my Trustees in their absolute discretion may think fit.”

I guess the questions are:

Does a non marital partner have an interest/prospective interest?

If they don’t, does the trustee still have a power to let them stay such as a general law power? Or are the trustees only able to let the beneficiaries live there?

I’m thinking there might be some general law where a partner is allowed to live there for the sake of the beneficiaries ‘best interests’.

But on the other hand, it’s the late parents house, if she was here she’d probably say “if you want to live with your partner you need to get your own place”.

The other beneficiaries not happy with it. Does the trustee even have a power to let them be there? I'm guessing if they don't then the partner would be trespassing?