Actually, this will work against your parents. What if your father needs medical attention while in the US? If you do not have insurance or your insurance is not good enough, then there is a potential for government liability.
The best thing to do is to try it the old fashioned way. Show links to India by showing property, income source, bank balance etc.
If your father is coming to the US to seek medical attention, then it is an entirely different case. However, the B2 visa is for tourism and if you show that your father is not having good health, but is seeking a tourist visa, it would not sound credible.
Just my opinion though ...
