OP
As regards the question, not enough information is given to offer a meaningful response. There are a series of questions that need answers:
1. What actually happened when the father died?
2. What actually happened when the mother died?
3. In whose name is the land currently registered?
4. Has there ever to date been a formal vesting of the land in anyone?
5. if not, why not?
You would think in this day and age that people would deal with land formally but regrettably there is often still a reluctance to spend the necessary money in formalising estates.
Section 125 of the 1965 Succession Act may be of assistance and that is set out below but, really, it is a matter of going through the various stages to truly ascertain the correct position and how it should now be dealt with.
mf
"125.—(1) Where each of two or more persons is entitled to any share in land comprised in the estate of a deceased person, whether such shares are equal or unequal, and any or all of them enter into possession of the land, then, notwithstanding any rule of law to the contrary, those who enter shall (as between themselves and as between themselves and those (if any) who do not enter) be deemed, for the purposes of the Statute of Limitations, 1957 , to have entered and to acquire title by possession as joint tenants (and not as tenants in common) as regards their own respective shares and also as regards the respective shares of those (if any) who do not enter.
[GA]
(2) Subsection (1) shall apply whether or not any such person entered into possession as personal representative of the deceased, or having entered, was subsequently granted representation to the estate of the decease"