The issue is with the photographer for not sending your mum a copy, usually with professional photos you don't get them on disc as its very expensive which is why your brother may not have put one up to see. It would be simple enough for you to ask rather than turning it into a big deal, its like when you give someone a gift voucher you don't expect too know what was purchased. TBH I would be horrified at at somone to ask to see my photos even if they were the one who arranged it.