Is the homosexual act with a brother in childhood considered Zina (unlawful sexual intercourse), and if so, how can one atone for this sin?

Sodomy is one of the most heinous abominations, and even more so if committed against a brother. Allah punished the people of Lut with a severe punishment for this act. The crime of sodomy is more repulsive than adultery, and the Companions unanimously agreed on executing both the perpetrator and the one upon whom it is perpetrated, regardless of whether they are married or unmarried. There is no connection between slave ownership and this indecency. If these acts were committed by you as an adult, then repentance and seeking forgiveness are obligatory upon you. If they were committed by you before puberty, then repentance is not binding upon you, for the Prophet, peace and blessings be upon him, said: "The pen is lifted from three: from the sleeper until he awakens, from the child until he reaches puberty, and from the insane until he regains his sanity."