Where in France can I find my French relatives?

I'm thinking about taking a genealogy trip to France someday to look for my relatives from one of my French ancestors born in 0900 A.D., in Paris. But I need to know where I need to go in order to do that. So please, if you know of any genealogical societies or libraries in France that will tell me where I can... show more I'm thinking about taking a genealogy trip to France someday to look for my relatives from one of my French ancestors born in 0900 A.D., in Paris. But I need to know where I need to go in order to do that. So please, if you know of any genealogical societies or libraries in France that will tell me where I can find my French relatives, please tell me what they are. Thanks!
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