Insane is right Cheley Hokanson. It's not a coincidence though as royals married royal and nobles married nobles and royals married nobles. vise a versa. It seems only when conquering or when money war machinery, eg., boats, arrows, and weapons of the ages, is the only time when new blood was brought into the fold.
Some exceptions were for instance the Danes/Vikings conquered France, the King's daughter became Ragnar bride and soon ruler of Francia.
His brother Rollo became the ruler of Normandy, most of us are related to him, Norseman Rollo and later his son William Longsword. This family blood is in the English heritage because they conquered most of England at one time or another, became Christians and went forward and multiplied, ergo, US! In a nutshell