I shouldn't think so but you never know...the sites listed suggest neutering at around 6/8months, so to be on the safe side, have a chat with the vet, and arrange that 'little op' asap!!
www.catclinic.co.uk
www.moggies.co.uk
www.catkinrescue.co.uk
We have 4 cats. Mother, father and 2 kittens(other 2 kittens are with my sister-in-law).When the father was just 6 months old he's fathered the 4 kittens. The biggest surprise was we though he was a she.
I couldn't have been any other cat as they were indoor cats in a flat on the 7th floor at the time.