Just to clarify. Rainer Hempel's book although an excellent and highly recommended book, contains many errors in the family listing as is always the case with genealogical works in progress.
Matthias Sommer was not married twice. There were two different Matthias Sommers in Philadelphia and the one who married Maria Magdalena Aldmann came to Philadelphia after our Matthias had married Christina Null (Nullin is the feminine gender form of the German name Null). The original Monckton Township settler's list from 1767 shows Matthias' wife as Christiana.
Unfortunately the whole Maria Magdalena myth has stuck around in many people's family trees so it's hard to clear this up for everyone.