if the "burden" is a Judgment Mortgage, and if the husband and wife owned the property as Joint Tenants (which is likely, as opposed to Tenants in Common) then the Judgment Mortgage would fall away for 2 reasons. Firstly, it is more than 12 years old. Secondly. it falls away under the "survivorship" rule i.e. his wife is deemed to own the property outright. As a judgment mortgage is against the husband's "interest" in the property, the Judgment Mortgage falls away as the husband no longer has an "interest" in the property.
If the burden is a registered charge, then it remains in place,
It is possible that the husband's estate has other assets (e.g. insurance policy)that might cover the liability to AIB.
Jim Stafford