"If we don't remind him of it, he forgets to eat."
Translation:Si on ne le lui rappelle pas, il oublie de manger.
"Nous" should be accepted since it's the translation of "we". I suppose the sentence was first written in French with "on" and the English one is a mediocre translation. With "on", anyone could remind this guy to eat. A better translation would be "If one doesn't" etc. But since "on" is often used instead of "we" in spoken French, they decided it was good enough.
My understanding is that the direct object always precedes the indirect object. In this case "him" is the direct object and "it" is the indirect object. So the correct order is le lui. To confuse things, the Duolingo dictionary defines "le" as "the", "it" or "him" whereas "lui" is defined as "him","to him", or "to her". It would seem that the dictionary should also include "to it" as a possible definition for "it". If I'm wrong on this than will someone correct me please.