Marrying stepfather Stepchildren

Question
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There was a friend asked about the legal marriage with a woman his own stepson. For that let me ask: Can a stepfather to marry with her ​​stepson? beg legal basis.
 
Answers
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It should not be when it comes to his mother, if had never been associated with it can. But not to the contrary.
Legal Basis
MAJMU 'Juz 16 HAL 218
دليلنا ما روى عبد الله بن عمرو بن العاص رضى الله عنه أن النبي صلى الله عليه وسلم قال (من نكح إمرأة ثم طلقها قبل الدخول بها حرمت عليه أمها ولم تحرم عليه ابنتها).
Our proposition is what is narrated by Abdullah Ibn Amr Ibn al-Ash that the Prophet said: he who is married to a woman, then mentalaknya before dikumpuli, the mother married woman is forbidden, but not haram for her son.