Kittens destined for pet homes get neutered before they leave my home at 12 weeks, so they are typically 10 weeks at the time of neutering.
Waiting with neutering till the kitten in 6 months or otler is not necessary. Your vet should get updated.
http://catvet.homestead.com/EarlyAlter.html
Are kittens placed in new homes at 8 weeks where you live? I am very sorry to hear that - they should stay with their mother and siblings till they are at least 12 weeks old.
Camilla