Depends whether the mother's parents are still alive. What about her husband? Assuming that those parties are no longer alive, the beneficiaries would be the 3 children.

As such, her half share would be divided equally among A, B and C.

The other way around it is for A to pay some monies to B and C. Thereafter, A, B and C can execute a Deed of Family Arrangement whereby parties agree for the half share to be transferred to A only, making A the sole owner of the property. 

That would be a practical solution. 

So now there's spouse and issue (children)?

Well, under the Distribution Act, it would be divided like this:


if an intestate dies leaving a spouse and issue but no parent or parents, the surviving spouse shall be entitled to one-third of the estate and the issue the remaining two thirds