Kay, unfortunately 1819 is about 3 decades before civil registration began in IOM, so there won't be any parents given. They were of-age (over 21) too, so no parents consent needed. The most you'll get is the witnesses. I may even have this somewhere deep in my files, but not recorded on my database.

I have Margaret Gelling's parents, grandparents etc, which I can send to you privately.

Obtaining Matthias's likely father, John Callow's will of 1835 would be very useful. Even better would be to transcribe it and donate to the will list.