I'm mildly curious as to who you're talking about when you say "he" ...
Jan could be either He or She. Doesn’t say on his/her home page. Pronounced “Yan” or “John” if he. I’m old school - in the absence of positive knowledge, I use the masculine form.
I guess pretty soon, that could get me fired or arrested...
Google the name, you get a king of Poland. Who knows?