Entity framework 7 relationships (friends of person and group of friends)

Question

I'm playing and Learning EntityFramework 7 RC1.

I have

public class Person
{
  public long PersonId{get;set;}
  public ICollection<Relation> Friends {get;set;}
  public ICollection<Group> Groups{get;set;} //Works if commented
}

public class Relation
{
        public long RelationId { get; set; }
        public long PersonId { get; set; }

        public Person FriendWith { get; set; }

        public ICollection<RelationType> Status { get; set; }
}

public class Group
{
        public long GroupId { get; set; }
        public long PersonId { get; set; }

        public string Name { get; set; }
        public ICollection<Person> Friends { get; set; }
}

Everything works in my model but not the last property of the Group class.

What i want is that a person can have Friends(Person) and can group his friends in groups (coworkers, friends...). The top would be to have the possibility to query a Person and get : - Person.Friends - Person.Groups - Person.Groups.FirstOrDefault().Friends

Thank you very for your help.