i think sometimes you just have to let things play out, if he wants to talk about himself people will see that and they will know what he is like so you are probably not alone with this,
i have to admit i am a bit of a hard hitting talker but i never cross that line,
they say the pen is mightier than the sword but i say the tongue can be even sharper, so use your wit and be smart about this, dont let it take over and drag you down, you are strong and your sister knows it so you have nothing to prove.
anyway i hope you had a good day, lots of people have been feeling down i think because its Easter and here i am trying to make it good lol 
‘oh well’ if you cant be a saint be a sinner as they say lol