I have noticed that a lot of Indian people talk to each other using English. I particularly noticed this in Mumbai, and later realised that in Mumbai there are a lot of different cultures of India and English may be their only common language.
The family I met on the train to Goa were speaking English with each other when they first got onto the train. When chatting with them they revealed that they family are originally from Gujarat, which is their first language, but they also speak Hindi and English.
Whilst walking on Elephanta island I noticed an India couple with 2 small children. They all spoke in English. The parents spoke English with a Indian accent, but the children were almost accent free. I assume that the parents have raised their children speaking both Hindi and English. It think is a very good thing to do. Children speaking fluent English will have a wealth of options available to them as they grow older.
Of course the only common language in India is English. Hindi, Tamil and Urdu and very different languages. When people from the north and extreme south of India met, English is the only common language they have.