Hello Lesley,
you search still in times of "data privacy protection" - only a descendant
will get answers - and he or she will have to prove, that he/she is a
descendant.
Here are the Links, which I would use - but they are in German - I did not
find them in english - but look yourself.
http://www.frankfurt.de/sixcms/detail.php?id=2952&_ffmpar[_id_inhalt]=518769
4
http://www.frankfurt.de/sixcms/detail.php?id=2952&_ffmpar[_id_inhalt]=518769
8
the following link is in english
http://www.frankfurt.de/sixcms/detail.php?id=2952&_ffmpar[_id_inhalt]=521214
2
I think a register extract is what you want - you have to know and pay the
prices - scroll down.
It would be helpful if you would know the district, birthname and the
birthday of your mother in law.
Good luck - I hope this was helpful
Christine