Friends, some advice, please!All is not well in paradise.My partner's youngest son (23 going on 17) lives in a granny flat on the property. You have to walk past his front door to get to ours. Luckily we dont have  heaps of visitors because the path is strewn with car parts and tools (all left out in the rain), there is rubbish and empty bottles everywhere. He also has two cars in various states of repairs.And because he doesn't have a working vehicle he is using his father's old car which we were going to sell. He is supposed to pay rent, but because he doesn't work full time the arrangement is that he do jobs round the place in lieu of rent.Unfortunately he is usually too busy swimming in the river or something, to do much. Another thing which also upsets me is that he will wander into the house without knocking. At the moment while his father is literally busting a gut to set up his new workshop and move all the stuff from the old one, what is boy wonder doing???? He's partying with his mates in the flat, they are playing duff duff music which is really pissing me off.The problem really is that his father, my darling, is far too soft on him and just wont do anything about it. I've only been with him for three years and have only recently come to live here so dont feel in a position to do anything or say anything.Help me please - any advice would be really appreciated.(btw I know the most crucial thing here is the stress it's causing me - not that this boy is thoughtless and lazy!)