My cousins wife is my supervisor

I work at a warehouse and another associate called the aware line complaining that I work under my cousin's wife. My HR said we can't work together because we're considered in laws, but I never heard of an in law cousin before. I feel like they're stretching here. To be fair we don't even know each other like that. I don't hang out with them or see them at all. Can any truly verify if this goes against policy. I just moved to this department and would hate to go back to my old department.