Simio and his son Junior in the El Rey de Los Gorilas (1977) movie
El Rey De Los Gorilas (1977) is a memorably bad Mexican movie which happens to be a Mockbuster adaptation of Fiction House’s Kaanga (pronounced Ke-Anga) comic. Thanks to its memorable Mexican following, it has both a rare dvd release on Amazon and a Tubi page: https://tubitv.com/movies/532571/el-rey-de-los-gorilas
The story revolves around a bunch of gorillas adopting a likely American orphan nicknamed Simio, who in turn grows up to meet a lonely local boy from a village inhabited by his fellow discontent Plant Men. A decade later, Simio himself meets a British survivor named Eva, who in turn gets acquainted with him. They later have a son whom I dubbed Junior in their own stilted treehouse. Later on, Junior grows up to meet two other subjects likely from South Africa, which used to be a part of the British Empire and was a Dutch colony before that.
Even though their hairstyles are quite different, I do believe that Simio and his preteen son Junior are ardent loincloth wearers.