My kids I definitely would, and some friends and family I would too I suppose.
When I was about 20, before I had children, we had been out drinking and my friend Chris was standing on a road bollard and it buckled and he fell off it, landing on his head unconcious in the middle of the road. At this very moment an enormous lorry appeared round the corner going too fast to stop. I pegged it in the road and my normally meek self managed to drag him to the curd bot safety. The lorry had slammed on its breaks but didn't stop till 10 ft past where he was lying. If I had stumbled whilst doing it I could have easily died and given how clumsy I am, its a wonder we weren't both killed.
I think in your mind you say no, I would risk myself for him/them but your instincts set in and you do. Its like that guy who waded in at the cash machine and got shot. Or women who say they would just be quiet until a rape was over, they shout and scream for help.