Mills and Boons

The story is about two people who have known each other since they were kids and were going to marry different people but ended up marrying each other.

With a contract that if either of them falls in love with someone else, they will dissolve the marriage and give a no-questions-asked divorce.

Both are career oriented. The heroine's mom worked at the hero's house and was also his fatehr's mistress.

The guy's name is Blake or something.