Question Summary:
Permissibility of eating in a restaurant where liquor is served.

Question Detail:

A family member owns a restaurant where they sell alcohol and allows customers to drink there. Is it permissible to sit in such a restaurant and eat? 

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
It is not permissible for a Muslim to sell or serve alcohol in his restaurant. Furthermore, it does not behave a Muslim to eat in such a restaurant, irrespective of the restaurant being owned by a family member or anyone else.
 
And Allah Ta’āla Knows Best
Immad Bin Arshad
Student Darul Iftaa
California, USA
Checked and Approved by,
Mufti Ebrahim Desai.
www.daruliftaa.net