I imagine they just tweaked the spelling of Han so that people would pronounce it correctly. Many English-speakers would rhyme Han with "pan," and that is not how the family says their name.
After all, since Korean uses its own writing system, it's advantageous to transliterate names into our alphabet in any way which makes them more clear.
I had a Korean student once whose surname was Bang, and he complained that people here pronounced it like "Bang! Bang! You're dead!" I suggested the spelling Bong, but I don't know if he considered changing it.
This message was edited 10/20/2015, 5:57 PM