marriage and family

My understanding is that a bhabi is the wife of one's older brother. That is, what we would call a sister-in-law here in the United States. This is someone who is completely genetically unrelated to you, as is her brother.

While it may be against your culture, I doubt that it's illegal in India, but you'll need to check of course. And more importantly, does this guy want to marry you? You could certainly marry here, but I'm not reading anything here that says the feelings are reciprocated.