Picture of the Herman Elte school, Amsterdam, 1928.
Probably the full name of Leo Engers is Leonard (born 1920) and of his brother Johnny: Joseph Isidor (born 1921). Their class mate Jette Pais remembers that they had a younger brother, probably called Henri, and that their mother died at a very young age. This may explain why they were in the same class.
See also under their father's name Isidor Engers and their names on this website.
Addition