Robert Le Shearman/Sherman b. 1281 - an earl?

[Daffodilica]

I've just browsed my Shearman line on Ancestry, and a few of the leaf hints sent me off in the direction of a Robert Le Shearman, b. 1281. I've Googled him and several websites call him 'Sir', and 'Earl of Yaxley'.

I've no idea yet whether this person is actually an ancestor, but how do I find out whether someone was an earl? Is there a definitive website I should look at?

Thanks!

[hallmark]

http://thepeerage.com/i3316.htm#s47511

[hallmark]

http://thepeerage.com/i3306.htm#s47398

[Daffodilica]

Thanks - can't find him on there. Oh well!