Laravel 5: one to many relation with more then one related column

Father.php

<?php namespace App\Models;
class Father extends Illuminate\Database\Eloquent\Model {
    /**
     * Get all children that call model their father.
     *
     * @return array
     */ 
    public function children() {
        return $this
            ->hasMany('App\Models\Child', 'id', 'biological_father_id')
            ->orWhere('stepfather_id', $this->id);
    }
}