You would only need to use Form 2120 if you are claiming someone as a dependent who you (with a group) provide more than half of their support. Your child most likely would not require Form 2120.
If TurboTax Online is trying to make you feel out this form, you can delete the form by doing the following:
- Log into your return.
- In the left hand navigation, click on the Tools link.
- In the Tools box, click on Delete a Form
- In the Forms list, find the Form 2120 and click delete.
This should remove your issues with this form.