Savannah, You're a little bit short on detail.
If the charge is a registered charge in respect of a loan, it remains as a burden on the house until paid
If its a judgment mortgage, it expires after 12 years
The questions are :
Who inherited Billy's house ? Was it is wife ?
If its a registered charge and the house was NOT inherited by Billy's wife, then its likely that the executors of Billy's will or the inheritors
will not be able to sell Billy's house without first removing the burden ( ie repaying the loan)
I would also be investigating if the loan may have been repaid earlier but the parties neglected to remove the charge
If the executors of John's will are digging their heals in and Billy's house has to be sold, then maybe a negotiated compromise might
be reached