Drunken Responsibility

Today my sisters came home incredibly drunk. My sisters fiancé looked after my sister with the patience of a saint. I tried to help, but after a while it started to annoy me, firstly because I'm younger than them and secondly I just really wasn't in the mood to be looking after drunken people. What are your views? If you are sober and a member of your family comes in drunk, do you have an obligation to look after them? Or do you not because have they done it all to themselves? What would push you over the edge to stop looking after someone? Have you had any experiences like this? Liam - What Lé Duck