I think there may be an error with "grand-parents" in the first sentence. All the references I have seen say it should be "grands-parents". The adjective "grand" in this case apparently should agree in plurality with the noun "parent", even though it doesn't agree in gender i.e. "mon grand-père" and "ma grand-mère" are "mes grands-parents".
Dictation exercise A1
Merci Paul, c’est corrigé!
Agree with you - Académie-française lists «grands-parents», and Robert (en ligne) refers to des grands-mères. Also see link:
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