Most people do not take care of their family because they think it's in their best interests. They often take care of their family for myriad reasons--e.g. a moral call to selflessness, sociocultural norms, a sense of familial duty, love, etc. The language of "best interests" really doesn't fit here.
Taking care of an ailing parent is in no way connected to maximizing one's returns on anything (except maybe fulfilling a sense of what you "ought" to do).
Taking care of an ailing parent is in no way connected to maximizing one's returns on anything (except maybe fulfilling a sense of what you "ought" to do).