Question: Could somebody have 1/3 ancesters of the nobility? In other words, could there be a individual whos ancesters are in one thirds of nobile descent?
1/3 is 2/6 is 4/12.
The formular for the largest possible number of ancesters is
2^n
While n is the number of generations backward. You have one father and one mother, because n=1 2^1=2.
You have, I hope, 4 different grand-parents 2^2=4.
The serie of this numbers go: 1,2,4,8,16.
No room for a 12. Bad luck?
Not necessarly because 2^4 is the generation of the grand-grand-partens.
Could it possible, what somebody lose 4 different grand-grand-partens due to merriage of cousins?
Yes it could, if it happend two times, right?
So, by abstract thinking, we came to the conclusion that it could be possible that one person is of 1/3 nobility descent.
In this way, you would lost 4/16 = 25% of your potential ancesters 4 Generations ago by cousin marriage.