Maintenance of father in law.

An old man, a widower, has a daughter, who is married. The man is also a part of a joint family consisting of two brothers and a sister. The sister is a spinster, while the brothers have their families. The brothers have retired on pension. Now this old man subsists on a private monthly pension plan, enough for him to survive. They have their own house and some land in a city. This man had used up all his youth on his paternal family, getting his brothers and sister educated and employed but did not devote much time towards his own family, his daughter or his wife. As a result, his daughter has had just basic education, without a scope for a decent employment. Having married her off sooner than normal, this man never even looked after the health of his ailing wife, as a result of which she died. Now that this old man is ill and his recovery being uncertain, with high medical bills and cost of treatment, is it the duty of his unemployed daughter and son in law who, by the way, have their own family, to provide for this old man indefinitely without much hope of getting inheritance by the way of property etc.? Or should his brothers and sister also look after him?