My dog is only friendly with my mum and she can only handle her. He gets annoyed always whn anyone touches him

Though it was me who bought this 3 mnth old pup ( cross of dauchand and stray one) but now he is almost four years old and never lets me tough him. Only few ppl can caress him, like my mum or an aunt. Whenever i go to home, he really gets happy to see me and jumps on me but the moment i touch him he starts growling. He even doesnt let my grandpa ( who lives with us) to touch him. Now that I am married i stay with my hubby since last two years but the matter has only gotten worse. He doesnt take food from anyone but my mum. And also starts to get excited by seeing strangers and at times end up scaring many new comers. He is otherwise very intelligent and understands everything my mum says..and behaves like an angel infront of her..Why this partiality?? Anyone facing same prob? I have tried to play with him..offer treats..but no use..he wont let me/anyone else touch him..