According to my information, Samuel Whitbread was apprenticed to a John Wightman, brewer in 1736. Was the name Wightman spelled Whiteman in those days? I have found no mention of the name Wightman or Whiteman on the Whitbread family trees, but I would agree that it is possible that John Wightman could have been known to the family from his possible links to Bedfordshire.
I would be interested to know more of your Whiteman/Wightman wills which were witnessed by Whitbreads. Could you give me the date and name of the will and the name of the witness?