There is book that I read years ago and I can't remember the Title or the author, so if you know please help me out!
In the beginning of the book the heroine is at a party where her cousin is getting engaged. (The cousin's fiancés is really a spy along with her brother) In the first chapter, the cousin finds his fiancés looking through some paper and he realize what she was doing so he beats her. Her brother(whom everyone thinks is her cousin and lover) kills him and they leave. The heroine met the brother outside and he made a past at her.
Then the heroine's father dies and she has to live with the uncle(who is a bad guy). Apparently the heroine father was helping the government un cover something and when she goes into the office that was her father she finds a envelope on the back a cabinet. She also finds the brother there and he takes the envelope and her in the carriage escaping the uncle's guards. When they are a good distance away they argue and he starts seducing her. Then she makes him stop and when the uncles and his guard come she gives the wrong direction where the brother escaped.
I don't really remember what happen after that some how the uncle get drunk and want to rape the heroine but her slave stops him but he rapes her. Then the uncle sends the heroine to England and the brother goes after her. While there she stays with some other family member and their son falls for her and teaches her how to sword fight. Then when she try to escape he tries to kill her but the brother comes and saves her.(b/c ahe escape her families house b/f he had a change to get there).
She goes back with him to America. Also his sister (the cousins fiancée) has a secondary romance with I think another spy(she is barren by the way). After they go back to the South, the brother want to uncover the uncle and he does but the heroine end up going also with his sister behind his back. She end up shaken because I think some how she fought with the uncle, and then you find out she is pregnant.
At the end both couple and a double wedding, where 2 American presidents(don't remember which ones though I think one was Adams) participate in the wedding.
So if you know what novel this is or even have an idea please let me know