He has repented from interfering with his sisters’ daughters – what should he do?

I am a 28 year old man. When I was young I used to interfere with girls, at the instigation of my older brother, when I did not understand anything. This continued until it became a habit. I started by interfering with my sisters’ daughters when they were small, until they grew up and refused to allow it, and it went on until my first years in university, when I became religiously committed and regretted it greatly. I became the only religiously committed person in my family. I pray in congregation and advise others and I do all kinds of good deeds, but I am unable to offer advice to my sisters’ daughters if they do anything wrong. I am wondering if my repentance will be accepted? This matter may have been a wrong that I did to my sisters’ daughters, my sisters and my family. How can I right that wrong and purify myself? People like me are subject to severe punishment in this world and are given a stern warning with regard to the Hereafter. I am very afraid and I regret it deeply. There is no power and no strength except with Allaah.

Praise be to Allaah.
We praise Allaah for having guided you to become religiously committed and righteous, and to repent. We ask Him to forgive you for the wrongs that you have mentioned towards your sisters and their daughters. You have to pray for forgiveness a great deal and do many righteous deeds, and keep away from the things that lead to sin.

The door of repentance is open, no matter how great the sin, as Allaah says (interpretation of the meaning):

“Know they not that Allaah accepts repentance from His slaves and takes the Sadaqaat (alms, charity), and that Allaah Alone is the One Who forgives and accepts repentance, Most Merciful?”

[al-Tawbah 9:104]

“And verily, I am indeed forgiving to him who repents, believes (in My Oneness, and associates none in worship with Me) and does righteous good deeds, and then remains constant in doing them (till his death)”

[Ta-Ha 20:82]

Repentance erases that which came before it of sin, no matter how great or how many the sins. Allaah says:

“Say: O ‘Ibaadi (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allaah, verily, Allaah forgives all sins. Truly, He is Oft‑Forgiving, Most Merciful”

[al-Zumar 39:53]

As for restoring rights, you have to make a lot of du’aa’ and pray for forgiveness for those whom you wronged, and Allaah accepts the repentance of the one who repents.

And Allaah knows best.