Thank you for the question. The circular patch can go for a patch of eczema. This is often aggravated by scratching and I think it would be advisable to tell your brother to refrain from scratching. Applying moisturizers to the area also helps the eczema.
Eczema also responds well to topical steroid creams.
If the patch is persistent, you can consider visiting your doctor to get it properly assessment. A fungal scraping may be ordered to rule out a fungal infection if necessary.