I am a phone caller. I am too impatient for letters. LOL But you have to do what you are comfortable with.
I agree with the masses, that communication with him is something that you should do. He may have been told a thing or two for his part in telling you her number...but he's an adult and on his own, so he doesn't have to tell anyone that he's heard from you again.
Good Luck.
Sorry your bsister doesn't want to get to know you.
