Very rude cousin

My cousin is 14 and is the rudest person ever to me and my mum. Whenever he comes over he waits for us to say hi first and if i was in the garden smoking for example he wouldn’t come and greet me, he would go straight on the sofa. Whenever me or my mum ask him a question he literally cannot say no, he just clicks his tongue. My aunt always blames it on the people he hangs around with but I know for a fact that muslim boys and men treat their family, especially women with respect. He doesn’t clean up after himself, and when he does it’s done very shittily. He has no respect for me or anyone for that matter and when I try to have a conversation with him he just stares at his phone and mumbles shit. He’s a teenager so he sweats a lot and he STINKS, and whenever I tell him to shower or at least wash his feet so our whole house doesn’t smell like shit my mum just says ‘leave him alone’. The thing is that my mum chats utter shit about him, but literally won’t say anything to his face or even tell him off. I’m honestly so tired of it.

Rant over sorry I just had to let my feelings out lmao