The absolutely grammar-nut correct ways are "different from", "similar to", "compared with". But UK, AU etc usage has grown to accept "different to and compared to". According to http://data.grammarbook.com/blog/adjectives-adverbs/different-from-vs-different-than/ "different than" is found in English texts as old as 300 years.
hmmm....no. There is a girl, who has a brother and HE is different from her brother. In French Il est different de son frere means he is different from his / her brother. The word "son" can refer to the subject's own brother, to male third party's brother or to a female third party's brother. There is no way of knowing. Therefore this sentence / translation is correct.
Sorry to stick my oar in, but ‘different from’ is actually the right answer grammatically (in British English, at any rate, and what I was brought up to say), even if many people use ‘different to’ and apparently in the US ‘different than’ (which sounds plain weird to me). I think DL were trying to teach the grammatically correct version.