I have no idea why you'd think anyone would avoid your questions but just to be polite & fair I plugged in to a simple google search of " William I the Conqueror biography" & found this info:

William I, King of England, commonly called William the Conqueror, was the illegitimate son of Robert, surnamed Le Diable, Duke of Normandy. He was born in 1027, and succeeded to the Dukedom on the death of his father in 1035.

on this page:

http://www.sacklunch.net/biography/W/WilliamTheConqueror.html

for you.
It appears his father was surnamed Le Diable.
There is more info on that page and on this site there is info, a timeline & more links:

http://www.yorkist.com/bios/content11.html

Hope that helps....

Terri