Connection

Need help on a puzzle from you guys... im totally stumped...

there is a connection between all four when you have the right answer to each. Here are my four things that connect, and yes i know they are vague, hence why im getting nowhere

A - a revolutionary
B - a French Departmental Capital
C - A Royal Family
D - Michaelangelo

now ive no idea on the answers or connections despite using google for considerable lengths. But for example B maybe Dijon and the others might fall into line and the connection could be Mustard.... Thats the type of thing im after. But id need to know your four answers to each and the connection that makes it work.

Any constructive help?