Jackie Ashenden - S3, 4
You are mine, Mine to take, Make you Mine, Kidnapped by the billionaire.

A new author for me.  Her books have gotten better and better with each one I read.  In the above series there is a continuing back story through each one as the romance develops with each couple.  It is well done and interesting.  A couple took a little to get into but once there you are hooked.