I am as well but like with a lot of celeb profiles who are connected with the tree, you have to go back 6 or 7 generations before you find any siblings listed. A lot of time it's the direct line only. So I'll bet some people are more closely related to some of these notables and don't know it.
So just the other day, I added all the siblings of John Wayne's paternal grandparents. I do that from time to time, add siblings to ancestors of notables.
Much to my surprise, I found that there was a double family marriage in the Morrison family. The sister of his Paternal grandmother, married the brother of his Paternal grandfather.
On a side note, we should do more than simply connect notables to the tree, we should attempt to fill out their familys more completely. For example, Actor Lee Marvin is said to be a close relative of Robert E Lee, but his ancestry on wikitree doesn't indicate that.