What is it about Mothers and their sons? really, what?

I have an older brother who only lives an hour away,an hour and he never ever rings or calls down to check on his parents. My Mum will ring him and text him or leave a voicemail but he never answers. Us siblings also get ignored unless we physically go visit. He has days off where he could come home and do odd jobs around the house or just visit mind you when he does once every 6mths hes always texting his stupid girlfriend so he may as well not be here as hes not listening when hes checking his mobile every 2secs! It annoys my Dad no end but Mother will always make excuses up for him and forgive him for not answering when she calls or texts 50 times a week.We have had it out with him each of us but sadly he just doesnt seem bothered.