No such thing as exempted from NS unless you fail the aptitude test or something. My 2 cousins are legit exempted because they have low IQ. Unless you’re medically unfit or psychologically unfit, you’ll never be able to escape NS. Deferment, yes. Never exempted just because he became a father or if his father is the MP or President.
Exempted or deferred? Is not easy to be exempted. Usually conditions such as severe mental conditions or permanent physical disabilities can be considered for exemption. Another possibility is he is not Singaporean.
Was he exempted or was his NS deferred? If it’s the latter, I think that’s possible...