as per various HC and SC judgements unamarried who are studying and treating married sisters customarily also is a part of duties of an earning hindu male and can be deducted from his income before deciding his share of maintenance for wife , father , mother and children.
old parents even if getting some pension and having serious illnesses are entitled to a share of maintenance which may in some cases be more than wife or children . a hindu male is duty bound equally to maitain his wife , parents and children as per law.
Please note : i am not replying to anyone , i am just adding to my earlier post.