My immediate family wouldn't ask to borrow, if my sons or daughter asked I would either give them it or go buy them something suitable. Whats mine is my wifes so to speak although I have taken back guns and given her something simpler that she likes better.
Family outside the above. Don't even ask, isn't going to happen.
I really don't like borrowing other peoples guns, would never feel comfortable with more than a few test clips or cylinders at the range. Basically if you lend me a firearm, I am responsible for it and will return it to your possesion in the exact condition I borrowed it in. Hence I have undue concern whenever I have it.
On the flip side I expect the same. I have been in situations where I have had both to borrow and lend guns. Always in hunting camp where some failure ended up leaving a hunter without a firearm. I am never on the recieving end anymore because I carry spares. In these circumstances to a responsible party yes.
For self protection, I doubt it, but circumstances dictate. In my past I have worked in some very low rent crappy places similar to Iraq. If you were with me and I thought you needed to be armed, I would hand you a firearm, make sure you knew how to use it, and pray you didn't. If I got it back later that would be a bonus. Most scenarios here in America I don't consider that dire and I would be extremely hesitant on arming someone, I'm not saying it could never happen but it would be a extremely rare situation.