Dear Princess,
I used to fight with my brothers, as you say, over dumb things.
I think I did it mostly to get attention from my parents. I would get started with my brothers, and they would yell at us. Attention is similar to love which is similar to respect.
Of course I can't say your Brother in Law is like me. But if he is, the formula for hadling the fighting is to avoid adding to the pay off, which is emotional reactions from others.
I did not hear the word "Please" in your request. I imagine that your tone of voice betrayed your irritation with their inconsideration.
If you son is sleeping, pin one of his socks above the clock so people know to be considerate. Or some other visible signal, that you would like fighting to be done quietly.
Find ways to boost Brother In Law's self-esteem, so He does not feel he needs the substitute of attention.
Sit down with him, and set up a signal word between you, that the arguing has crossed your line of reasonableness, and you would like him to cut back making his points for now.
ODD is Oppositional Defiant Disorder, and the techniques for those teenagers are helpful.
http://www.docspeak.com
You are speaking in terms of punishment, rather than in terms opportuinities for negotiation.
Here is the negotiation sectin of marriagebuilders. com May have some ideas for you.
http://www.marriagebuilders.com/ubbt...t=0&Board=UBB3
Blessings