How do Weeping Angels reproduce? Are the cherubs supposed to be juvenile Weeping Angels?
There is not information (that I could find) about how Weeping Angels are created. I can think of a few ideas of how they reproduce:
Like @Valorum said in the comment, if they reproduce like humans (aka sexual intercourse), they need to make sure there is no eye contact (turning the lights off or closing their eyes).
There is a possibility that there is a finite number of Weeping Angels (no one says they reproduce. The babies, for example, may not be babies but just look like that).
They may be a result of something we don't know about (like the big bang or some sort of sonic sculpting).