From Longman Dictionary of Contemporary Englishgood luck to him/them etcgood luck to him/them etcused to say that you hope someone is successful, even if you think this is unlikely ‘They’re hoping to finish it by November.’ ‘Good luck to them.’ → good
Examples from the Corpus
good luck to him/them etc• All I say is: good luck to him.• And all good luck to him.• Big women can be as fit as anyone else and if so, good luck to them.• If they start talking high teens, good luck to them.• In which case, good luck to them both. 