Change beneficiaries class in a irrevocable discretionary trust

Dear all,

I got a trust deed which states:

" The Trustees may from time to time and at any time by any written instrument or instruments:
(b) with the consent of the Protector declare that any person or persons nominated by the Trustees shall thenceforth be included in the Specified Class …"

At the end of the Trust Deed the beneficiary’s class is defined as:
" Mr. XY and/or his family members"

Now the Trustees want to add also a friend of Mr. XY as a member of class. Do they have this power? or it the power just related to persons who fit the family member test?

thank you in advance,