I dont know title or authur but I loved this book. Please help.

They are a secret sociaty with speical powers. The girls parents both had powers but she didnt. Her mom dead for a while and dad just died. She had helped him in his work, keeping people & their powers in a liberary or something. The main guy can control the weather and he is mad about a war in scotland and the coucel thinks he is going to try something stupid so they make him marry the girl so she can keep an eye on him & report back to them. He thinks  she is nice but not very attractive but he can only go to scotland if he marries her, so he does. After they are married she starts looking better to him and soon he is in love with her and cant explain it. Now whenever they meet any men they are all attracted to her and he is getting man about it. they figure out that she is a temptress, that power does not make itself know until the girl is married and after first sex. she tries to keep him out of trouble.
 
Thats all I remember but it was a great book and I would love to find it again. Please any help would be great.