In relation to the handing down of the family "papers". I think it is important that any family member who wants a copy should get one. Hence more of a chance that they will survive into the future. As far as originals go, you have them in your custody now and as with anything else you have, you have the right to hand it down to whom ever you want to. Just because your nephew doesn't want to serve in the military, please don't rule him out. He may well be the person that has the most interest in exploring the family history. (only you know your family)

Now onto his choice of tartan. You have not listed any reasons as to why he wants to go for the female line. I gather he is not trying to gain some title or position that your family may or may not have had. I suggest you let him explore that side, in fact help him, I am sure that the more he learns and his increasing maturity will also get him interested in the male line too.