Q: In brief,
someone stayed in seclusion with his brother's wife,
which had evil consequences.
It is impermissible for you to stay in seclusion with your brother's wife or to talk with her because of the contingent evil consequences you referred to. Moreover, you have to repent and ask Allah for forgiveness regarding what happened. Moreover, you are recommended to be frequent in performing acts of obedience such as Salah (Prayer), Sawm (Fasting), recitation of the Qur'an and the like. Furthermore, you have to stay away from evil-related places. May Allah accept our repentance and yours, for He is All-Hearing and All-Near. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.