BlueRose
Oh my! That sounds so like my mother (and father, too). I have a younger brother who never sends anyone birthday cards, Christmas cards, etc. When my mother was still alive, she kept telling me to call him, send cards, etc. One day my father started in and I told him that since my brother doesn't send us anything, why should we send him something? My parents knew how to manipulate--"two wrongs don't make a right"--true but there comes a point where you say why do I get the guilt trip? When I was a kid, I couldn't say anything when I was ordered to write or call someone but when I became an adult, I felt freer to speak up. On my wedding day, after the ceremony, we were all at my uncle's house to continue the celebration. My mother took me aside and pointed out an elderly distant relative and ordered me to go to her and thank her for her gift. This was a relative that I hardly knew-it was my mother's idea to invite her. I told my mother "no, I'm not going to" and told her forcefully. She backed off but I later found out that she made my husband go talk to this person.
Speak up and tell your mother that your brother doesn't acknowledge your existence so why should you be forced to do what she tells you? Sure, she will give you a hard time but hold your ground. I learned to do that. If my mother heard that we were vacationing in a particular city, she would try to order us to call someone that she knew who lived there. Again, I would say "I'm not calling that person". If she demanded to to know why, I would say that I really didn't know that person and she should be the one keeping in touch, not me.
Years ago, my parents separated for a few months. My aunt (mother's sister) believed that my husband and I were spending more time with my father when in reality we were trying to be fair about things. However, my mother told lies to my aunt regarding this. After my parents got back together, my aunt treated us horribly for years. We would send her a Christmas and a birthday card and she wouldn't acknowledge it. I would call her and she would cut me short. She warmed up some when my daughter was born. Fast forward to now--we recently visited her and out of earshot, she weepily told my husband that she wanted us to visit her more! Apparently, she forgets just how horribly she treated us!
On the flip side, as a mother to a young adult daughter I every so often hear from relatives who ask me why my daughter isn't keeping in touch with them. All I do is relay what they said. My husband also reminded her that they are family and do care about her and that she should make an effort to keep in touch. To the relatives I say that we relayed the message and that we did raise her properly. However, she is an adult now and on her own. Your mother needs to know that about you, too. Incidentally, your brother is also an adult. Again, keep holding your ground. If you do decide to keep in touch with your brother, it should be your decision and yours alone. It sounds like you tried and he is indifferent. Whatever happens, you can always have the satisfaction of knowing that you tried.