public interface IMaterializable
{
    void OnMaterialized();
}

public class MaterializedInterceptor : IMaterializationInterceptor
{
    public object InitializedInstance(MaterializationInterceptionData materializationData, object instance)
    {
        if (instance is IMaterializable materializable)
        {
            materializable.OnMaterialized();
        }

        return instance;
    }
}

public class MyDbContext : IdentityDbContext
{
    private static readonly MaterializedInterceptor _materializedInterceptor = new();

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    { 
        optionsBuilder.AddInterceptors(_materializedInterceptor);
    }
}

public class Father() : IMaterializable
{
   public int Id { get; set; }
   public string Name { get; set; }
   public Daughter Daughter { get; set; }
   public List<Son> Sons { get; set; }

   public void OnMaterialized()
   {
        // Id and Name are loaded
        // Daughter and Sons are not loaded
   }
}

public class Son() : IMaterializable
{
    public int Id { get; set; }

    public string Name { get; set; }

    public void OnMaterialized()
    {
    }
}

public class Daughter() : IMaterializable
{
    public int Id { get; set; }

    public string Name { get; set; }

    public void OnMaterialized()
    {
    }
}

public void GetFathers()
{
    Father father = await _dbContext.Fathers.Include(b => b.Daughter).Include(i => i.Sons).FirstOrDefaultAsync();
    // father.Daughter and father.Sons are loaded
}