A "tit for tat" attitude never made anyone feel good. Quit comparing and enjoy your life, including your sibling in laws. If they are carrying a bad attitude ... that is NOT your problem... but when you carry this bad attitude, it makes you feel bad.
Quit comparing and keeping score and enjoy your life by being loving and generous.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.