What was the connection between the royals of Britain Russia and Germany?

They were all large European countries. I'm not too sure about England, but Prussia, Austria and Russia teamed up to eliminate Poland early in the 19th century.

NEW RESPONDENT

They were the main States which militarily opposed to France, starting from the outbreak of the radical phase of French Revolution, until the fall of the First French Empire in 1815.

During that period they formed seven Coalitions, of which only the last but one and the last one fought successfully.