Is it obligatory to confess to one's parents about engaging in pre-marital sexual acts with a sister, or homosexual acts with a brother, if this occurred during childhood without their knowledge or under duress, and how does one repent from that?

Children who have not reached the age of accountability are not held responsible for any reprehensible acts they may commit, due to the saying of the Prophet, peace be upon him: "The pen has been lifted from three: from the insane person until he recovers his sanity, from the sleeper until he awakens, and from the child until he reaches puberty."

As for adults who commit a forbidden act, they must repent and conceal themselves. Parents should nurture their children, guide them well, and pray for them.