Another vote for definitely not a requirement, but of course, a very nice thing to do. I think it should depend on the relationship as well. I did get my neice some "big sister" books when her sister was born. I plan on giving my son a gift from his new brother when he is born. I will also have my son pick out a gift for the baby. I have no expectations of anyone else giving a gift to my son.
At some point, children need to learn that they don't get gifts everytime someone else gets a gift.