Why does my cat pee and poop specifically on my clothes?

Three months ago, our cat started peeing and pooping on my mother's clothes in the basket in the laundry room. We haven't done any major traveling recently, or changed his litter/food. He is two years old and neutered. We pay plenty of attention to him, regularly clean his litter box (it's automatic), and make sure he has plenty of water and food. It's a two cat house hold, with 5 people living in it. He only urinates/defecates on my mother's clothes, no one elses. We're moving soon and we'll have to get rid of him if he doesn't stop. (not put down, just sent to our grandma's house in the outskirts of town.)