So you invite someone to be your long term house guest, a sibling, knowing their sexual history, while they get back on their feet after falling out with their father, who they were living with. But ask that they have an std test as you know they have had unprotected sex with approx 20 partners total (some unprtected) and this makes you feel uncomfortable about catching something from a shared bathroom. Is it ok after 3 weeks of them not getting tested, or showing signs of getting tested, to ask them to use a different bathroom/toilet to you and your partner?