Can the sole beneficiary keep me from seeing a copy of my father's will? what rights do children have?

Lots of good information in the other answers. I just wanted to add that you'll catch more flies with honey. If there is something of your dad's that you really want to have, then approaching the "sole beneficiary" and simply asking for it, nicely, may get you what you want. Could save a lot of time, money and heartache by handling this as a personal matter. Good luck.