My sister (17 years old) gets PIP and her and her BF have recently moved in with her dad, sister, dads gf and her son. Dad & GF get UC and other benefits, my sister who is 17 is going to be added to their UC claim, her BF who is almost 18 will not be on their UC claim. I suggested carers allowance to him for caring for my sister and her dads GF shot that down by saying it will impact their benefits / council tax etc. so can anyone help me with any advice on if him getting carers allowance whilst not claiming any benefits will do anything in regards to others in the household please

thank you