be aware that the capital gain may be subject to the kiddie tax form 8615.
Who Must File
Form 8615 must be filed for any child who meets all of the following conditions.
1. The child had more than $2,500 of unearned income (this would include the capital gain, if any on the sale)
2. The child is required to file a tax return.
3. The child was under age 18 at the end of 2023,
The son's return cannot be filed until the parents' return is completed because the form requires certain information from their 1040.
https://www.irs.gov/pub/irs-pdf/f8615.pdf
