A Quokka Dreeds its Weird

Somehow, some prince and his wife die, leaving behind their young son. The wife's friend takes the kid in and raises him as her own. They end up moving from place to place, trying to avoid the royal family (I forget why) but eventually the kid's uncle (the prince's brother) finds them. Of course, he wants his nephew, bu the chick is reluctant to give the kid up. I guess the prince really needs a convenient wife or something, so they come up with the genius plan of getting married. This will allow them both to have custody of the kid and allow the prince to have a nice trophy wife. (I think the heroine resists this idea at first, but the prince points out that she pretty much kidnapped the kid in the first place, so if she doesn't agree to the bargain he can have her up on charges of kidnapping the royal heir). Of course, they eventually fall in love, blah blah blah. Not exactly a groundbreaking idea, but after reading ten consecutive novels that all appear to have the same plot (man and woman fall in lust, conceive a baby, get married for convenience, then fall in love) anything that deviates slightly from the norm by introducing somebody else's kid as a plot device sounds pretty darn creative.