OCD controlling my sister

Hi I need advise my nephew has OCD but he makes his mum go through every ritual and it is very exhausting for her she has to stand while he tells her when to speak when to close the fridge door when to get him a drink,he was tested for drugs but wouldn't do a urine sample my sister is totally at hers wits ends he won't shower and is living like a homeless person his room looks like a drug den so my question is can someone with OCD bully and make another person carry out these rituals or has the OCD occurred because of drug taking any advise appreciated as my sister and I are really concerned