As long as you have not been issued a stimulus check, meet the eligibility requirements to receive a stimulus check, and they are under 17 as of December 31st, 2019, then yes, you may be able to include them in your stimulus check amount.
Please see the following link to determine how much your stimulus check should be.
If you determine you should receive a stimulus check based upon the above link, you have a couple of options:
If you already filed your tax return for 2018 or 2019, you do not need to do anything. The IRS will issue your check using the information on your return
If you are not required to file a tax return, please use the following link to register with the IRS as a Non-Filer