They separated 20 years ago - judicial separation only came into existence in 1989 which is 20 years ago. It is entirely possible that the separation was informal and prior to the 1989 Act, in which case your mother is entitled to her share (1/2 or 1/3) under S111 of the Succession Act, 1965 (have a look at the following sections too).
Separately you might be entitled to make a claim under S.117 if your father "failed in his moral duty to make proper provision for the child in accordance with his means, whether by his will or otherwise"
But I get the feeling your mother knows a couple of more facts than you do.
Separately you might be entitled to make a claim under S.117 if your father "failed in his moral duty to make proper provision for the child in accordance with his means, whether by his will or otherwise"
But I get the feeling your mother knows a couple of more facts than you do.