The cynic in me says that the brother who gave the cards was flustered (in case you find out he was giving the other one preferential treatment) and goofed. Having said that, why do you even expect a gift from him, since you know you are second best; unless he is the richest sibling with money to throw around? Do you give the two of them gifts that are equal in value? Or is it tit-for-tat with you? I'd call him and say there was a discrepancy between the value on the card and the actual value of the gift - a public service, just in case, you know, he finds that his bank account is missing a few pounds.