My brother and I are supposed to be splitting the costs for our mom's care but he keeps finding reasons why this month isn't good for him financially, and I think he's fallen into thinking that since I make more money it's somehow more fair for me to pay more, but we never agreed to that.
More people experience this than they realize.
Differing financial circumstances are triggering fairness biases that override your original agreement about shared responsibility.
“Where Are You with Behavioral economics — biases in financial decisions?”
If this sounds familiar, the Library can help you find the bigger picture.