I'm writing a Marauder Era fic in which a Slytherin and Remus Lupin, not too quickly, but fairly easily become friends. What I'm not positive about is the significance of the difference in house. I remember reading that the the severity of house rivalries always fluctuated over the years but I don't even know where to begin looking for that information.
Considering the hostilities between Snape and the Marauders, and the fact that the Deatheaters were organized and/or became active almost immediately upon the Marauders leaving Hogwarts, I am not clear on what part parentage would play in chosing one's friends while at school those years.
I've continued writing as though at that time, families such as the Malfoys and Blacks were considered extremists and that it wasn't so unheard of for students in different houses -even a Gryffindor and Slytherin to be good friends.
Anyway, hoping for some imput and different perspectives.
Another thing I've taken into account is that my original character is female. And with the exception of Bellatrix who I'm sure gladly enlisted if not took a large part in the organization of the Deatheaters, I don't know that many pureblooded daughters are given the choice to join. I may be wrong about that, too. I'm just back from a very long fanfic break :b