You have done nothing wrong and it's entirely possible that both of you will get a refund. Your tax situations are entirely different. The tax and refund is based on all your other income, all the credits/deductions that you qualify for, and any tax withheld.
As long as you have gone through all the areas in TurboTax, the program calculates your refund based on your individual situation. The same goes for your son. You don't have to fix anything in TurboTax.
"Why all of us got a refund from IRS?" This year, there are many changes to the tax law due to the Tax Reform, the standard deduction is doubled, for example, many taxpayers will benefit from that change; possibly you as well.
