ANSWER:

It is not permissible to have such mixed gatherings of non mahrams. 

You must arrange segregated rooms for men and women, not only while eating but for the whole evening. Men must sit separately and women must sit separately. 

Sheikh, my not immediate cousin but bit distant cousin will be coming over for a meal, is it permisable for our families to sit together but not next to her husband and her sitting next to my brothers as we eat together or do we all have to sit separetly so women with women and men with men? Please advise