Yes it is a sin to mix at a place for any purpose with the opposite gender when you have an option of sitting alone.

I am in my uncles house temporarily. No woman wears hijab inside this house. The maid enters upon us or passes by us when we are eating at the table.The man servant also does the same.The manservant does not listen to me.No one cares about sin.My parents call me to eat at the t(only my mahrams at the table).Is it a sin to eat here?I need yes/no answer please