Jewels of Historical Romance question

I am looking for a historical romance that I read years ago about a lady that thought she was married to a man who was holding her brothers health over her. She sold a dagger to an Earlier, I think he was an Earl, named Marcus. They fell in love but she wouldn't be with him because of her supposed husband. Marcus found out she wasn't really married from his friends and went and got her. That's all I can remember but I would love to read it again. Thanks in advance!