2 life tenants, death of first life tenant with no explicit provisions

I am dealing with an estate where the executors/trustees are directed “to pay the income of the residuary estate on trust to such of x and y as shall be living at my death and if both of them in equal shares absolutely.”
The remainderman provisions state “Subject to the above, my trustees shall hold my residuary estate on trust for z absolutely”

y has now died and the drafting does not make it clear whether the whole of the income of the residuary estate is paid to x or if z becomes entitled to the capital of this half share.
Does anyone have any thoughts please?