Does FIN stay the same if you move back to Singapore

I used to live in Singapore as a child in the 1990s and had a dependent pass under my dad’s employment pass. A few years ago my dad moved back to Singapore with a new job. I am now also in the process of moving to Singapore for work and the MoM has asked for my old FIN which I don’t have given it has been 20  years and I was a young child when we left. It has been suggested that by giving my dads FIN they may be able to find the record of my FIN.
My question is:
Is my dad’s current FIN the same as the FIN he had in the 1990s or will he have been given a new FIN when he moved back so this new FIN won’t help them find my records. If it has changed I don’t want to give the new one as it will just confuse things more.
(Have asked my dad and he doesn’t know if his current FIN is the same as his old one or is a new number. Have also emailed my old schools and embassy of my country and they don’t have records of my FIN)