Does your family live in the UK on a permanent basis, ie it is their 'home', or do they hope/expect to go back to Pakistan in the near future to live there on a permanent basis?
Furthermore, by deciding to forego the option of obtaining UK citizenship, did they take into account the benefits of having a UK passport that they were opting out of, eg visa free travel to virtually all of the Western countries (as compared with a Pakistani passport), the ability to go and live/work anywhere in the EU (until Brexit is finalised anyway)?
Forgive me for being a bit dubious about your statement, but perhaps by answering the questions above, you could provide further clarification?