@feruze-- Skin bleaching creams scare me. I think those are very dangerous. They can cause weird side effects like thinning skin and loss of skin pigments. I think you should steer clear of them.
Have you tried natural remedies? I highly recommend products with vitamin C first. Vitamin C has brightening effects on skin. You can use lemon juice on your groin area and keep it on for fifteen-twenty minutes before washing it off. My sister takes a lemon and scrubs her dark areas with it in the shower. She says it works. You can also buy body creams with vitamin C.
My mom says that if a part of skin doesn't get enough oxygen, it will darken over time. I used to have this problem with my underarms. Ever since I started wearing more sleeveless shirts, the tone of my underarm skin has improved. You should wear shorts at home to let your groin area get plenty of air. We are always wearing tight jeans nowadays and I think our skin doesn't like that.