How to query Entity Framework objects where select is a list

I am trying to do something simple, but I can't figure it out. Using EF6, I have 2 tables which are associated by an intermediate associative table, giving a many-to-many relationship:

I want to query all users who belong to a list of families. So I get an array of families:

var db = new MyProjectEntities(); 
User user = GetUserById((int)HttpContext.Current.Session["CurrentUserId"]);
var families = db.Users.Where(u => u.UserId == user.UserId).First().Families.ToArray();

Then I want to query all users belonging to these families:

var users = db.Users.Where(u => families.Contains(u.Families));

But I get this error:

Instance argument: cannot convert from 'Database.Family[]' to 'System.Linq.IQueryable>'

Thanks in advance.