You don't qualify for the capital gains exemption for sale of a personal home. You didn't live there 2 years and you aren't selling early due to an unforeseeable circumstance. However, you probably have a stepped up basis equal to the fair market value on the date of your last parent's death (August 2023). So your capital gains will be based on the gain since August 2023, not 2015 or earlier. It depends on exactly what is meant by "retaining lifetime rights" and you may want to discuss it with a tax professional.
