Oh, man, we should totally sit down someday and discuss at length the dynamics-of-writing-Remus-and-Tonks! This is something I think about a LOT. I love the characters of Remus and Tonks, both individually and together, but given what we've got to work with from canon, it can be quite a challenge to write them without it turning into an unhealthy relationship of a sort I would cringe to see a friend of mine in in real life. (And of a sort which I don't in any way want to be advocating, especially knowing how many impressionable young folks read fanfiction, and how much creepy/awful/unhealthy stuff there already is out there!)

Oh, believe me, this was even more of an issue in writing the HBP half of this story. Ugggh, canon, JKR, why.