Will a young man who follows up on matters concerning the sponsorship of an orphan receive the same reward as the sponsor, given that his mother is the one who pays the money because he is a student?

If your intention in sponsoring an orphan is sincere, accompanied by effort and attempt, then you hope to attain the full reward of sponsorship, by the grace of God. For Islamic law stipulates that a person with a firm intention, who does what they are capable of, receives the reward of the complete doer. This is indicated by what Shaykh al-Islam Ibn Taymiyyah said: "If a person acts with a firm intention to the best of their ability, they are, in Islamic law, in the position of the complete doer: they receive the reward of the complete doer." This is also supported by the Prophet's (peace be upon him) narration about the man who wished he had wealth to do good deeds like another person, whereupon the Prophet said: "He is by his intention, so their reward is equal."