Does having an adult child living with you affect your UC

Hi, my sister in law son wants to move back home to help look after her. She is struggling financially and is struggling with her health. But she is worried that it will affect her Universale credit. He will not be paying rent but he wants to help out and pay electric and gas bills and pay for the weekly shopping bill. This would help her a lot but she is worried that it would affect her universale credit. She lives with her husband who is off work at the moment and receives SSP and she gets the enchanced carers allowance from UC. She receives around £520 a month from UC, and he receives £360 SSP. They will be coming off Universal credit in around three months when he is fit to go back to work. Her son earns Gross around £350 a week.  She would love to have him come and live with her but not if it affect her UC, and would wait until they come off UC. Can anyone explain if this would affect her UC payments