Odd if he were adopted in Ireland he would be using his birth name and birth certificate or indeed would have known his birth mothers name, children given up for adoption in Ireland are given new names and an adoption certificate in place of a birth certificate. Adoption certificates do not refer to birth mothers or father's at all. Adoption was and still is shrouded in secrecy in Ireland. Police should exercise caution here, lots of Moriarty's in Ireland , lots of chancers too! It's possible although slim possibility if his mother was unmarried he was not adopted out but cared by extended family or friends or had been unfortunate enough to be placed in state care when very young until he was eighteen then he left Ireland immediately for the UK and onwards to Australia.
REALLY interesting and helpful to know. Thanks so much for that!