That could also be this incomplete series that sounds more like this in the later part of the series:
The Weathered Series:
1.
Weathered1.5
Murphy's Law2.
Crawling in the Dark2.5
Again3
Sweet Child (WIP hasn't been updated since Nov 2006)Good series, but it's been awhile since I read it, so the details I'm remembering could be mistaken. Very similar to Kallysten's To See the Sun Again. But I could swear it's this one because I remember Buffy and Spike go searching for their daughter. I'm not sure but maybe their first daughter. That's where the details are sketchy, but I do remember in Sweet Child they were looking for her, found her, but it didn't go down exactly how they wanted it to...and that's where you are left hanging. Amazing WIP, but so sad it never was completed. I'm not sure about the royalty Spike part though...again it has been awhile since I read this series.