Is it possible to receive the reward for sponsoring an orphan by caring for a sick, bedridden widow?

Taking care of a needy mother-in-law and serving her is a righteous deed for which the doer will be rewarded, as stated in the Almighty's saying: "And whatever good you do, Allah is All-Aware of it," meaning it will not be lost with Allah. There is no evidence that the reward for this act is equivalent to the reward for sponsoring an orphan, but the reward is obtained from two aspects: attending to the mother-in-law's needs, and enabling and assisting the wife in showing filial piety to her mother.