You say that this is an arranged marriage. That sounds strange. I have not heard of any nepali family arranging a marriage with an Indian. The only exception is Pyar Jung's daughter, but that's a special case. Also, I don't understand how the family backgrounds can be similar. I mean an indian household is very different from a Nepali one. Can you provide some clarification here, and I might be able to provide more insighful comments. Other than that, it all boils down to personal preferences. If the guy loves this girl that much, he should be willing to learn a bit of nepali. It shouldnt be too hard for someone who already speaks hindi. But i personally think that "everything else being the same," cross-cultural marriages require a lot of effort, so it's not gonna be smooth sailing.