I am not a tax accountant but I think you could file a joint tax return if you are married and you have obtained a tax ID for your wife. I think you have to ask your wife or parents to go to the US embassy at Kathmandu and stamp their Passport. They have to take I think W7 form filled with marrige certificate with them to stamp their passport saying that they are related (wife/son/daughter if they are under 21 years/parents) to you. I think then they have to send copy of the passport or paasport and you can get tax ID for them. Then you might be able to file jointly. If they are here or were here then I think you don't need to go to the embassy and get passport stamped. I hope this wil help you for your tax deduction question. If there are any tax accountants they can explain more. But I am sure you can do joint filling.