Social Security and Adult Disabled Child

My adult developmentally disabled son has been on social security since his father died when he was a minor. In 2023 I retired and in 2024, social security sent me around $15k for retro payments for the care of my son even though he does not live with me - he lives in a group home. They told me I was entitled to this money since I still provide financial support for my son who earned $5505 in 2024. Is this taxable to me? He wouldn't be a qualifying child since he doesn't live with me and I assume he wouldn't be a qualifying relative since he earned more than $5050 in 2024. Thank you in advance.