Jewish orthodox uncles are permitted to marry their nieces--although, amusingly enough, their aunts can't marry their nephews--that would be incest. All in accordance with biblical laws. This is common knowledge, and widely discussed. You can find this out with google in a matter of seconds. The history of the Rothchilds is repleat with it.
The Bible ruled out marrying your father's brother, your father's sister, and your mother's sister. It fails to mention your mother's brother. So it's not that it gives permission or approval, it just fails to mention it.
You know the Good Lord gave you some brains for a purpose. I don't know what certain orthodox Jews do, but I wouldn't advise marrying your uncle, no matter how hung up on him you are.
Lev 18:8 The nakedness of thy father's wife shalt thou not uncover: it is thy father's nakedness. ... 12 Thou shalt not uncover the nakedness of thy father's sister: she is thy father's near kinswoman. 13 Thou shalt not uncover the nakedness of thy mother's sister: for she is thy mother's near kinswoman. 14 Thou shalt not uncover the nakedness of thy father's brother, thou shalt not approach to his wife: she is thine aunt.