The same alias cannot be defined 2 times in the same query
$qb = $this->_em->createQueryBuilder();
$qb2 = $qb;
$qb2->select('m.id')
->from('Custom\Entity\MembreService', 'ms')
->leftJoin('ms.membre', 'm')
->where('ms.id != ?1');
$qb = $this->_em->createQueryBuilder();
$qb->select('mm')
->from('Custom\Entity\Membre', 'mm')
->where($qb->expr()->notIn('mm.id', $qb2->getDQL())
);
$qb->setParameter(1, $service);
$query = $qb->getQuery();
return $query->getResult();
Ideally you should use many-to-many relation for your entity, in this case your query is going to be much simpler.