Our ancestors appeared to use the following basis for choosing names for their children. You will find that these sort of naming patterns run through the generations - apart from modern times.  Although the latter is probably due to present day families being a lot smaller and being more fragmented.  Not forgetting the high divorce rate.  How could you apply this naming convention to half brothers and sisters?

 
First Son Father's Father
First Daughter Mother's Mother
Second Son Mother's Father
Second Daughter Father's Mother
Third Son Father
Third Daughter Mother
Fourth Son Father's eldest Brother
Fourth Daughter Mother's eldest Sister
Fifth Son Mother's eldest Brother - or - Father's 2nd eldest Brother
Fifth Daughter Father's eldest Sister - or - Mother's 2nd eldest Sister

It was not uncommon for a child to be given the name of an elder sibling that died as an infant - which can really cause confusion if the death of the infant is not noticed. So do check for infant deaths and and later births having the same given name.

Handed down names may comprise both given and surnames.  Maiden names were frequently passed down as given names.  Occasionally a maiden name was taken as an additional given name on marriage - the origin of hyphenated surnames maybe? If you find a given name that could be a surname - look for an earlier marriage between the two names. It can be very useful when trying to distiguish between contenders having very common surnames. This coupled with given name patterns can give really good pointers.

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