John Gill Commentary Joshua 21:33

"All the cities of the Gershonites according to their families were thirteen cities with their suburbs." — Joshua 21:33 (ASV)

All the cities of the Gershonites, according to their families Which were divided among them, according to the number of their families: [were] thirteen cities with their suburbs; two out of the half tribe of Manasseh beyond Jordan, four out of Issachar, four out of Asher, and three out of Naphtali.