Hi, I've been doing some research lately... I am descended from Susannah and George Martin through Hanna's sister, Ester.
Christopher Martin was married in England before his voyage to a first wife and had children. The son that traveled with him and his second wife on the Mayflower I believe was a stepson and older. They left their own toddler son with family in England. The practice at the time of the Pilgrims was to keep a child with the mother until about 8 and then have them live with another family for training. This would help bring up proper children and prevent them from being spoiled. A Puritan practice i believe. So,it might not be so far fetched to believe they would leave a young child behind and protected in England. Christopher Martin was not necessarily immigrating because of just religious reasons and had money and influence of some sort. He more than likely had children with his first wife. Both George and Christopher were from the Hampshire England area. Christopher would have been 48 when George s born. George would have been 2 when they left on the mayflower. I have not found the solid proof of the connection between Christopher Martin and George Martin.