What is the ruling on a brother harassing [someone], and is it permissible to commit suicide because of it, and what are the implications of a brother harassing a child, and is ghusl al-janabah (ritual bath due to major impurity) required for the child, and is it obligatory to inform his father, and what is the ruling on actions that may result from the harassment?

If your harassment of your brother was unintentional, then there is no sin upon you. There is no legal punishment (hadd) upon you that necessitates killing, and suicide is not permissible for you. You should take the initiative to marry in obedience to your father if marriage is lawful for you. Neither your brother nor the other child is required to perform ghusl (definition) (ritual bath). No sin will befall you if your brother or the other child deviates, as Allah Almighty says: "And no bearer of burdens will bear the burden of another." You should advise your brother and the other child with wisdom and gentleness.