Llewelyn

I think the only way anyone can pronounce the Ll is if you're Welsh! The best way I can explain it here is to put your tongue to the roof of your mouth and make a hissing sound.
As for the rest of the name, it's pronounced uh-well-in (Literally how you pronounce those words).
So add the hissing sound to the start of the sentence Uh, well in and you've got it!
I hope that helped, haha!

Living in the US I've always heard it pronounced like "Lou-ah-lin" but I'm sure it's different in Welsh. Either way I think it's a great old-timey, manly name.

I found a website that explains the pronunciations of Welsh names, and their advice for pronouncing the 'll' sound is to "put your tongue in the 'l' position and try to hiss".

Pronounced hloo-ellen.