I live in the USA and am the only son, and I have a married sister who lives with my 95 year old father in Pakistan. I want to bring him to USA and take care of him till the rest of his days. My wife believes that my father is not only my responsibility but also my sister's as she lives in my father's property.
You are responsible about your father. Do not miss this great chance to serve him in his old age and do not listen to any one including your wife if she wants to discourage you from serving your father.