My parents sacrificed an incredible deal to come to the US. For the life of me I can't comprehend why someone would do this. Loss of citizenship is permanent. Your kids lose it as well. Why would derek would do this to his kids.
Maybe he doesn't want his kids to have to deal with the U.S. I.R.S. every year of their life, regardless of whether or not they live in the U.S.? Just one of the possible reasons.
After all, it's not a burden on his children until they begin collecting income. If the concern is really for the children, it would be more pragmatic to give them sufficient time to make up their own mind.
No. Parents cannot, under any circumstance, renounce US citizenship on their childrens' behalf. If they gained citizenship at birth, they can only lose it by their own actions.
Perhaps he has decided to obtain Singapore citizenship? Singapore requires those who obtain naturalized citizenship there to renounce all other citizenships they hold.