Has anyone used a DNA Registry?

Well, since my half brother and I only share the same mother and she is deceased, it doesn't sound like we could get a definitive answer through DNA even if we could find him. I'm really kicking myself right now, because my mom died of cancer several years ago and, at the time, I had considered putting her hairbrush into a ziploc for future use if necessary. I wish I had done that. I know that sounds terrible. Hopefully we can figure out his birthdate or exact month/year.