try http://www.ee.surrey.ac.uk/Contrib/manx/famhist/genealgy/index.htm for an intro to records (+ links to a rather large website!)
Dont trust all you read - always ask who supplied the information and were they in a position to know (+ also allow for unintended errors) - eg offspring might not really know age of parents! (in those days of less bureaucracy possibly not important)

Unfotunately Kelly is the most common Manx name, Cowley is also a relatively common name. One point in your favour was the name Maria - generally seen as too Roman for most Manx.

German and Patrick are next door parishes - possibly both had connection with Peel ?