Hi Sara. Would you like to let us know please exactly which of the children you are looking at who were born before the parents? As far as I can see, father Gilbert was born about 1593 (unsourced), mother Isabel about 1603 (unsourced), and the oldest child John about 1617 (unsourced). The dates may be estimates, but if they are correct, Isabel would have been about 14 when John was born: very young, but not out of the question.