laravel-eloquent-relationships | eloquent relationships to Laravel php framework | Build Tool library

class PageRelation extends Eloquent
{
    public $incrementing = false;
    public $timestamps = false;
    protected $table = 'page_relation';
    protected $casts = [
            'parent' => 'int', // FK to page
            'child' => 'int',  // FK to page
            'lpc' => 'int',
        ];

    protected $fillable = [
            'lpc',
        ];

    public function children()
    {
        return $this->hasMany(Page::class, 'category_id', 'child');
    }

    public function parents()
    {
        return $this->hasMany(Page::class, 'category_id', 'parent');
    }

    public function siblings()
    {
        // ...  return $this->hasMany(Page::class ...
        // how do I define this relationship?
    }
}