If you are single and have no dependants, then you don't need life insurance.
You really have to look at the level of cover and the premium paid, to decide if they are good value.
Most mortgage protection policies have a level premium but a declining level of cover. So as they were taken out 15 years ago, the cover might be very small.
If you think that you need cover, then you should shop around and see if you can get the same level of cover for a lower price. Even though you are older, because the premium is fixed and the cover has reduced, you might well get cheaper cover.
And I presume you have no intention of taking out a mortgage again in the near future? If you did, you might be able to assign the existing policies to the new mortgage.
It's probably costing you very little anyway. It's just in case.
No problem with decreasing cover. Your 2 year old becomes more independent as they get older and the cost of care decreases. Also, you own net worth increases so the need for cover decreases.
It's not a problem as such but if it's not needed at all, then there is no point in paying for it.
Furthermore, as it was taken out at a fixed monthly repayment, he should check if he can get the same level of cover for less money.
But with a 2 year old, he needs to assess his need for life cover separately from the mortgage protection issue. And then see if the mortgage protection policy should be retained as part of his overall need for life cover.
If Frank dies while the child is still dependent, then there will be a mortgage-free house in the estate.