My online alias in places is Kysairshade, but people who've said is aloud always pronounce it 'Kaiser' for reasons I don't get. Then again it's not a common word so it's sort of unfair to expect them to get it right off the bat.
My last name is also french...written, you would never pronounce it right, and spoken, you would never spell it right, unless you were solely francophone, which even I am not. My family gives an improper pronounciation on purpose and readily accept it, but even then, it's very often misspelled.
The word is written Pepin. It is properly pronounced peh-pain, with the N kinda silent. But even said as written, peh-pin, people try to add an extra p or get pippen, pepper, etc.