My wife is worried that my four-year-old son is getting to attached to my mother. I am happy that he really likes his dadi but am also worried about my wife. What should I do?

Ask your wife to spend more time with your son. Children get attached to the person with whom they spend the maximum time with. Your wife can do fun activities with him, read to him, play with him, take him to the park in the evening. You three can go on outings during weekend.