Is it necessary to confess to the paternal uncle's wife what one has committed against her in the past (peeping at her and stealing her clothes) in order to ask for forgiveness, or is there another solution to deal with this sin?

Looking at private parts is forbidden by Islamic law, and it is more dangerous when it involves the husband's relatives. Sincere repentance is required, involving remorse and a firm resolve not to return to the sin, without a detailed confession of what happened. It suffices to ask for forgiveness from the couple with general phrases such as: "Forgive me if I have wronged you." Islamic law has forbidden looking at private parts and the entry of non-mahram (definition) women, emphasizing the danger of the husband's relatives, as Allah Almighty says: "Tell the believing men to reduce [some] of their vision and guard their private parts. That is purer for them. Indeed, Allah is Acquainted with what they do." (Surat An-Nur: 30), and as the Prophet, peace and blessings be upon him, said: "Beware of entering upon women." They said, "O Messenger of Allah, what about the Hamo (in-law)?" He said, "The Hamo is death." Hamo refers to the husband's non-mahram relatives, and being alone with them is more dangerous than with others. Likewise, intentionally sniffing good scents from non-mahram women or their clothes is also forbidden.