My GtGt Grandmother was Henriette Michaelis-Jena b. Detmold 1820 m Israel Heinemann Heimann 1842 and d 1850 in Luegde after giving birth to four children.
A generation back and several sibs were Michaelis, one Michaelis-Badt and Henriette's father Michaelis-Jena One more generation back and one brother is Jena and the other Michaelis!
I have a note but don't remember from where - that it was a way of distinguishing different branches of the family and is mentioned in histories of Westphalia.
There is a similar pattern in my Heimann family from Luegde where brothers take different surnames.
Jena is a town in Thuringia to which I have not come across a connection.
As we clearly both descend from Joseph MJ and Brendel Gerso. Treuenfels , I should be most interested to know more about the Ritschenwalde connection.
Hazel Dakers, London UK researching
BIRNBAUM &GOLD (Zgierz, Poland), HEIMANN (Luegde Germany & South Africa), MICHAELIS-JENA (Detmold ), NORDEN/NORDON/NORTON (London & South Africa) www hazeldakers.co.uk