A henry number shows the position of a person in a family tree, for example, the henry number 1712,3 , reading from right to left, shows that the person is the third child of the second child of the first child of the seventh child of the progenitor.
Henry numbers are useful in finding the degree of consanguinity between two individuals. If one or more of the first characters of their henry number are in common there is a relationship. My henry number is 1712,146,273,64. Comparing with the henry number first given it can be seen that they have the first four characters in common, we are related.
The person with the henry number 1712,3 is Gilbert, an unwilling emigrant to America. Our most recent common ancestor has the henry number 1712 and is Robert b1656, of whom my forebear was the first child, and Gilbert the third child, so that he is some degree of uncle. An uncle has a one generation gap, a grand uncle two generations, a great grand uncle three generations, we have a seven generations gap, which gives the relationship as 5xgreat grand uncle.
To take another example, George Jesse Bending, an early casualty in the Great War, has the henry number 1712,146,631,3. In this instance the first seven characters, 1712,146, are similar, this is the henry number of William, b1760, at Ottery St Mary, our common ancestor, George Jesse's 2xgreat grandfather and my 3xgreat grandfather. First cousins share a grandfather, third cousins a 2xgreat grandfather, and as there is a generation between us, we are third cousins once removed.
Henry numbers for the main Bending line have no prefix, for other lines there are four character prefixes. The prefixes of progenitors may be seen in the progenitors tables.
Where there are more than nine children, numbers are replaced by letters, 'a' for the tenth child, 'b' for the eleventh, and so on.