I was looking some baptism records once and found lots of apparent triplets being born. Then realised it was just delayed baptisms. Possibly as the fathers were seamen and it being tricky to get all the family together at the same time.
However with five children it is more likely, as suggested, that the parents (or one of them)may have been Quakers, Jews, Roman Catholics or whatever and then for some reason decided to join the Anglican church. This may have been precipitated by the vicar refusing to marry some person who had not been baptised. People being baptised and married the same day are not uncommon.