There are also no records of them having been born in Lincolnshire were the family are sure they must have come from. Just don't know were to go next. Does their marrage details list anything that can help, do you have access?
There is a baptism for a James Short abt correct time - in Lincolnshire -father Edward
This seems to be the james Short on the trees who is married to Charlotte Trim
but both trees do not have sources - so it seems to me to be nothing more than a guess
I think you need some certificateas to get any further - if the family member who has been researching states there is nothing on the certificate then how has he/she come to the conclusion the family were from Lincs??? Could you find out exactly what certificates the family member has???
Suz