Hi Spring 68
You, son, must have had an ongoing PIP award. These are reviewed after ten years regardless of the disability - so, yes this is normal.
You haven't said which type of review form your son has received. I am assuming it is an AR1. There is advice in the guide to PIP claims and reviews. You will find information from page 132 onwards on how to fill out the form. Once you have had a look, come back if you have any questions.
benefitsandwork.co.uk/guides-for-claimants/pip BIS
