idk if they are sterile but the general rule with hybrid offspring is they are highly variable
like, i saw this in a family of a friend... only the first child had black skin like dad but all the rest were pale
Discussion
Its also possible the mother was... less than ideally trustworthy...
no, the pale children were all otherwise typical austro-indoneesian skull shapes and everything, no, they had the same father
though you have a point, it could have been another austro-indonesian father, but they were all very similar personality and looks, just one was dark, the others were all pale