Question Summary:
Please clarify if I am my step daughters mahram .I am married to their mom and there biological dad is alive

Question Detail:

 
Please clarify if i am my  step daughters mahram .i am married to there mom and  there bilogical dad is alive.

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
You are a mahram to the daughter of your wife (your step daughter). As such, the laws of hijab will not apply between you. However, in this era of fitna we advise to exercise caution and modesty.[1] 
 
 
And Allah Ta’āla Knows Best
Saleem Khan
Student Darul Iftaa
Bradford, England
Checked and Approved by,
Mufti Ebrahim Desai.
www.daruliftaa.net