sabp26 (Ship 09/14 Div 002)

Yes, if he gave you the names then they are most likely in his division or his brother division. Either way, they have mail call together so yes, use the address you use when writing to your SR.  The last name only should be fine unless there is another SR with the same last name, but then your SR would have given you more info to help with that.  There is a place on http://callsforrecruits.org/ where you can provide info on recruits who need mail--from what happened a month or so ago, they give the names to anyone who requests names so sometimes the recruits get letters from 20 or more people, so it might be better if you write and maybe have some of your close friends write.

Do not post names openly.  You can PM names to people if they ask, but NEVER post the name of your SR or of any other SR or Sailor. Please remove the post in the  Boot Camp Moms group where you did that. Thanks.