I recieve correctly this two messages , but I need to JOIN this two results with Laravel5.

Could anyone helps to me ? Or it's any possibilities to doing this with other form?

$mensajes = Messageuser::find(1)->conversaciones()->get();
$mensajes2 = Messageuser::find(4)->conversaciones()->get();
echo $mensajes;
echo $mensajes2;

UPDATE

The MessageUser

use Illuminate\Database\Eloquent\Model;
class MessageUser extends Model {
    protected $table ="message_user";

    public function conversaciones(){
        return $this->hasMany('App\Message','id_message','id');
    } 

}

The Message model

<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class Message extends Model {

    protected $table="messages";

    public function chat()
    {
        return $this->belongsTo('App\MessageUser','id');
    }

}

UPDATED2

When I tried to sort in the view appear Illegal offset type

$mensajes = Messageuser::find(1)->conversaciones()->get();
        $mensajes2 = Messageuser::find(4)->conversaciones()->get();
        $mensajes = $mensajes->keyBy('created_at');
        $prueba = $mensajes->merge($mensajes2->keyBy('created_at'));
        return view('admin.msj')->with('pruebas',$prueba);