I think when you are referring to family members you don't use the article. But I could be wrong!
DL usually accepts contractions, even though their own sentences are often hopelessly stiff.
You may know by now, but singular family members don't need articles while plural ones do.
I miei fratelli.
Can the duolingo people speak English? I had “How is your mother going? Marked wrong. It suggested “how is your mother doing” as correct.