- Big Brothers Big Sisters, the premier youth-mentoring organization of the Oshkosh area, welcomes you. Since 1986, prepared adult volunteers have been bringing a little magic to children's lives through one-to-one and group mentoring relationships, which are supported by the organization's professional staff. Mission Big Brothers Big Sisters of Oshkosh Area will strengthen the future of our ...www.bigbros.oshkosh.net/index.html