I hear it all the time; it irritates me. My experience has been with african-americans saying it. I would only say "younger" if "younger" extends up into one's 40's and '50's. I do not hear it from A-A's who appear to be more educated, for the most part, unless they seem like they are trying to relate to another who uses it. Some A-A college students are using it, but that is a much smaller number. It's the same thing with the word "moms" - when talking about one mom. For example "Yo! Moms said you can't go!" Just my experience.