using System;

//-----------------------------------------//
public class Person
{
    public int Id { get; set; }
    //
    public Relative Relative { get; set; }
    //
    public Other Other { get; set; }
}    

public class Other
{
    public int Id { get; set; }
    //
    public int PersonId { get; set; }
    public Person Person { get; set; }
}

public class Relative
{
    public int Id { get; set; }
	//
    public int PersonId { get; set; }
    public Person Person { get; set; }
}

//----- context --------------------------------------//
public class CemeteryContext : DbContext
{
    public DbSet<Person> People { get; set; }
    public DbSet<Other> Others { get; set; }
    public DbSet<Relative> Relatives { get; set; }

    protected override void OnModelCreating(ModelBuilder mb)
    {
        mb.Entity<Person>()
            .HasOne(p => p.Other)
            .WithOne(o => o.Person)
            .HasForeignKey<Other>(o => o.PersonId);
        mb.Entity<Person>()
            .HasOne(p => p.Relative)
            .WithOne(r => r.Person)
            .HasForeignKey<Relative>(r => r.PersonId);
    }
}