What are good cardio exercises for slightly overweight 13 year old boy?

Overweight Teen. It's best to interest the youth in activities that he can enjoy such as swimming and team sports. You don't want to make the young man self conscious about his weight. Get him to choose an activity that is fun ! if he can choose the activity and have fun, the rest will follow. Finally, good nutrition (avoid the word diet) needs to become a family affair .
Playing. For young teens, there is no set exercise that is better. It is best to engage him in physical activities that he likes, decreasing the sugar drinks and snacks and eating more veggies and lean meats.
Exercise. Focus on what he likes and who he likes to do it with. Fun exercise that anyone can do includes frisbee or ultimate frisbee, mountain bike riding, kayaking, hiking to a destination, pick up soccer or basketball. At this age focusing on competetive sports is daunting, so team sports that include already developed skills like soccer can be overwhelming. Do it with him and enjoy!