8 yr old had untreated strep throat 5 weeks ago fever for 3 days sour throat for 5 i am worried he might get complications brother ws treated fr strep?

Risks involved: The frequency of complications from untreated strep vary from kidney disease that usually shows up early <2wks, to nervous system disorders, heart disease or rheumatic fever that shows up later >4wks.The combined risk is estimated at about 1% per individual infection but varies regionally depending on the strain in the area. You have ~ 10 days from 1st sx to treat & abort the long term risk.

Very unlikely: Local complication such as local abscess in throat occurs as infection spreads to adjacent tissue. Rheumatic fever occurs several weeks after "strep throat, " however, it's incidence in us has been very low.