Ok, if you've never watched TV, if you've never watched movies, if you never looked at your grandparents, if you never looked at kids on the street, you're going to be one heck of a strange creature. Have you never seen a person who is a baby, have you never seen a little kid, have you never seen your parents, your uncles, aunts, your grandparents or people this age walking on the street or at the store? I would think that you've seen people like this, or you've got to work on it.
Don't give up just because you don't personally have someone in your mind. Remember those movies; remember those TV shows, not so much the story, but the characters in the stories. Remember the family you saw in the store the other day when you pushed your trolley by and some kid was screaming their head off wanting to suck on the lolly pop which was still in the bag they couldn't open yet because it wasn't paid for.
You've got to stimulate your imagination. One of the ways to do reflections is to get the imagination going, otherwise you're just sitting there thinking "I can't do it, I can't do it, I don't know anyone that age. I can't do it." No, that's self-defeating, that's that negative self-image, and we don't want that. So we have to push ourselves to remember things. Push ourselves to recall certain stories we've read, in magazines where we've seen pictures of people. So work on that memory, work on that imagination and I think your reflection meditation will flow better and better as time goes by.