I say them both the same way "ah-ron", but I know some people pronounce
Aaron differently "air-on". Therefore I would probably use the
Aron spelling, so that people would pronounce it correctly. I pronounce
Erin differently as well "eh-rin".
I don't think it's particularly common. I've only ever met one
Aaron and he is 20.
The second A is a little unnecessary, but
Aron looks incomplete for some reason!