As a general rule of thumb, a baby shower can be hosted by anyone except the expectant couple themselves. This could be a close friend or group of friends, co-workers, church groups. In the past it was thought that only non-relatives should host a baby shower out of fear that it seemed the family was asking for presents. This thought should be thrown out the window, because throwing a baby shower is much more than presents.
A baby shower is a party for the pregnant mom herself. It is a time in her life where she can share one of the most important, exciting milestones in her life with her family and friends. Baby showers are a way for friends & family to share in that joy and make the mom and dad feel very special. Throwing a baby shower begins the first pages of memories that the mom can share with her child of all the preparation that was put into his/her most awaited arrival.
Therefore, it has become much more common for mothers and sisters of the expectant parents to throw the shower. The most important thing is that someone takes the honor of hosting the shower and sharing with the family. And what an honor it is to be a part of the celebration for the new bundle of joy!