Mom must have asked me 30 times yesterday does she have any brothers or sisters living..for the hour my brother was here she never asked..she did repeat a few things. But not that..she has been asking a lot bout brothers and sisters momma and papa, I wanted my bro to hear. But even when other brother called she repeated question but not bout her bros and sisters..my siblings think I'm overreacting cuz they r not here 24/7..
Perhaps you could draw a very simple family tree on a white board or a large piece of poster board, showing each of her siblings with a notation of the year they died or the town where they are living. Once in a while talk to her about it, but most of the time just answer simply, "Your brother Michael is living in Florida."
It is exasperating to get the same question over and over. You may be able to minimize this by writing common answers down, but the behavior itself is not likely to go away.
It is also exasperating that others can't see the depth of the problem. My husband was able to "showtime" when we had visitors and my sisters never did see him at his usual level of confusion. You can explain the concept of showtiming to your family, but I'm not sure how much difference that would make.