Question: Two boys who had not yet reached puberty went diving for water in a cistern (mājal). They went down and swam. As one of them was ascending from the bottom of the cistern toward the surface of the water, his head struck the belly of his companion. The one who was struck grabbed hold of the one who struck him, and both of them sank while in that state. Eventually, the one who was struck let go of his companion, so the one who struck him rose to the surface after his companion loosened his grip. He then waited for his companion, but he had died. Up until now the family of the dead child still do not know the true story, and the surviving boy is now a fully grown man. What is required of him?
The answer – and Allah is the One who grants success – is that this child, who is now a man, must pay the diyah from his own wealth alone, and nothing is upon his ʿāqilah, because the ʿāqilah do not bear liability in cases proven only by confession. As for fasting, no kaffārah is required of him, because at the time of the offence he was not legally responsible (mukallaf), and fasting is only valid from one who is legally responsible.
Yes, if this man fears the reaction of the dead child’s family when they learn of the story, then he should use lawful stratagems to cause the money to reach the heirs of the child, with each one receiving his share of the diyah, by any means. In this way his liability is cleared, and it is not a condition that they know it is the diyah of their child.
What may indicate this is His saying, exalted is He: “Allah intends for you ease and does not intend for you hardship” [al-Baqarah:185], and His saying: “He has not placed upon you in the religion any hardship” [al-Ḥajj:78], and His saying: “So fear Allah as much as you are able” [al-Taghābun:16], and His saying: “And do not throw yourselves with your own hands into destruction” [al-Baqarah:195].
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2