Laravel 5.7 getting all the siblings for each child - laravel

Question

I wonder how to get all the sibling that a child have in laravel model ?
I know i can use this $siblings = \App\Child::all()->where('parent_id', $parent_id)->where('id', $id); to get all the child siblings, but I want to know if I can do the other way or more cleanest way?
So you can call this in the blade view $child->siblings->full_name something like that.
But I wonder how to use it something like this in the model.php
public function parent()
{
return $this->belongsTo(User::class);
}
with only using the belongsTo or hasMany function maybe if it's possible?
Sorry I'm not good with english so I don't know what it's called so I can search it on google.
Edit:: Adding Child.php
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
use Carbon\Carbon;
class Child extends Model
{
protected $guarded = [];
protected $dates = [
'birthdate',
'father_birthdate',
'mother_birthdate',
'guardian_birthdate',
];
public function parent()
{
return $this->belongsTo(User::class);
}
// I want to call this function only using $child->siblings (this one will show all the siblings)
// without passing the parent id
// to make it cleaner
public function siblings($parent_id)
{
return $this->all()->where('parent_id', $parent_id);
}
public function getAgeAttribute()
{
return Carbon::parse($this->attributes['birthdate'])->age;
}
public function getFullNameAttribute()
{
return $this->attributes['first_name'] . ' ' . $this->attributes['last_name'];
}
}

Answer 1

There are 2 ways you could do this.
1 creating the below method:
public function sibling()
{
return $this->belongsTo(User::class)->where('parent_id', $this->parent_id);
}
2 using a single Query:
$siblings = \App\Child::where('parent_id', $parent_id)->get();
Hope this helps
Update
A third way is:
public function scopeSiblings($query, $parent_id) {
return $query->where('parent_id', $parent_id)->get();
}