I read a lot. After while, I start noticing similarities that might not be apparent to others.
The other day, I read "Girl in a Red Tunic" by Alys Clare. This is a series set in 1100's England. There are two protagonists; Abbess Helewise and Josse d'Acquin and, while both characters are in each book, they alternate as to who has the principal focus.
I wasn't far into this current book when it struck me that the series style is a Middle Ages version of S.J. Rozan's Lydia Chin/Bill Smith books. To be correct, I should state this the other way around as, I believe, the Clare series started prior to the Rozan.
What I like about both series is that there is not an intimate relationship between either set of protagonists, although some of us are holding out hope for Bill and Lydia. In each pairing, the characters come from very different backgrounds, yet have become friends and are always there for each other. And isn't that what real friendship is about.
I am certain there are many other series that reflect this same model. Come on in and let me know your favorites.