james/ severus relationship

[abhamghp]

No: HPFGUIDX 76350

I've been trying to catch up on posts, so forgive me if either of 
the following two things has been mentioned and I've overlooked 
them.  I've been listening to OOtP on tape; the first time, I read 
the book, and just finished hearing the chapter about Snape's worst 
memory. Anyway, I've tried to pick up on any subtleties, and two 
things struck me that I didn't catch the first time around.

1.  I think Lupin, Sirius, James, Peter, and Severus were all in 
Slytherin and were all in the same year.  I have noticed that there 
are five boys in the dorm; could it be possible that each year five 
boys and five girls are placed into each house?  I don't know, but 
I've noticed that Dean and Seamus are quite close, and obviously, so 
are Ron and Harry.  I wonder if MMWP and SS were in similar 
situation, and SS was a kind of outcast with his dorm mates as 
Neville has been to this point.  Many things lead me to believe that 
Sirius was in Slytherin, most of all parentage.  Could the Hat have 
considered Harry for Slytherin based on his parentage as well?  
James' actions in SS memory lead me to believe he is Slytherin 
material.  Wormtail is also Slytherin material for obvious reasons.  
The only one I can't quite figure is Lupin.
2.  It was quite disconcerting to learn that James was so evil to 
SS, even though 15 year old boys can be quite so.  I realize that 
this theory conflicts with #1, but I'm just thinking.  When Lily 
asks James what he has against Snape, he states something to the 
effect that the fact that Snape merely exists is reason enough to 
torture him.  What if they are brothers, perhaps?  That is the only 
relationship or even possibly excusable reason for torturing someone 
based on their mere existence that I can think of.

Thanks,
abhamghp