Is the Hadd penalty to be carried out on one who touched his sister's private parts without penetration, and is repentance sufficient after repenting from this act?

You must repent to Allah Almighty for this ugly deed, with remorse and a firm resolve not to return to it, for repentance is obligatory for a grave sin. You have the right to feel unhappy and ashamed, for a man protects his family and fights to defend his honor. This incident highlights the importance of raising children with good morals and values, separating them in beds, and keeping them away from the causes of vice. We advise you to conceal what happened and not tell anyone. There is no prescribed punishment for you, but rather sincere repentance, and increase in righteous deeds.