But this does not mean you must share a common bed and may be shades of gray---if the two of you have essentially separate areas, separate baths, separate kitchens, separate bills then it sure reads like two separate persons under common roof--basic roommates --but if this was a potential mate and you set up common house, common kitchen, common bath, and common bills etc---and perhaps the relationship won't go to marriage and may even be headed for rocks --but so long as it is not illegal under local law, its been going on for full year+ , and your housemate fits the low economic criteria and you pass the 50% + support test you may want to triple check the rules?
For that matter if the kid down the block was orphaned or no longer welcome at home and you took him in for 1 year plus and he had limited or no other support and you provided over 50% of the support (w adjustments for any foster care payments) you probably would be entitled to claim him as a dependent. Ditto for his homeless grandfather you took in over 1 year ago.