I would torture without ceasing and without mercy till my loved ones were once again safe at my side. I really don't think I would stop short of anything. If the choice is permanently disfiguring or crippling some thug or losing my wife or brothers or parents, then that's not a hard choice for me. I'd get medieval and in a hurry in this situation.
I just cannot understand the people who say no to this scenario. You'd really let your spouse, child, parent, or whatever die because you didn't want to harm a murdering thug? I can't understand that line of thinking. Just like I can't understand the extremist pacifists who say they wouldn't use lethal force to protect their children from a killer. I try and try to see their point of view, but I just can't. Its beyond me.
That said, this scenario is so abstract and impossible, I don't really see what insight can be gained by it.