Praise be to Allah.
The basic principle in spending on relatives such as parents and children is to be found in the Qur’aan, Sunnah and scholarly consensus.
With regard to the Qur’aan, it is the aayat (interpretation of the meanings):
“but the father of the child shall bear the cost of the mother’s food and clothing on a reasonable basis” [al-Baqarah 2:233]
“And your Lord has decreed that you worship none but Him. And that you be dutiful to your parents” [al-Isra’ 17:23]
Duty towards parents includes spending on them according to necessity.
With regard to ijmaa’ (scholarly consensus), Ibn al-Mundhir said: “The scholars are agreed that spending on poor parents who have no source of income and no money is an obligation on the son’s wealth.”
The obligation of spending is conditional upon the one who is spending being able to afford to do so, and upon the one on whom money is spent being in difficulty and being in need of that spending. This is according to general consensus.