Nigeria, Dec. 3 -- Six-year-old Yusufa Isah shares a makeshift wooden sleeping platform with Tijani Abubakar, 13, on this isolated cattle farm, about 40 minutes' walk from their family settlement in Osomo Village in Iseyin, Oyo State, southwest Nigeria.

The two underage boys lay on a mat half-covered with a mosquito net. There is no infrastructure or water or sanitation facility here.

"This is where he sleeps with the cows," says a mature pastoralist who only gave his name as Mohammed. He pointed his hand at Tijani, who looked up at intervals shyly. Yusufa hid in the makeshift home as though frightened at the sight of a stranger. The three individuals share an extended family tie.

Under Nigerian laws, as well as guidelines set under th...