"Mi tío y mi tía caminaban en esa calle todos los martes."
Translation:My uncle and my aunt used to walk on that street every Tuesday.
i switched uncle and aunt, and got it wrong. it could be regional i suppose, but i have never heard "uncle and aunt". it sounds funny to me, although not techniquely wrong.
This is what's called a "collocation": like saying "salt and pepper" instead of "pepper and salt". Aunt and uncle is the only correct answer because it is the way you would translate this sentence, and not each word.
Why isn't "my uncle and my aunt were walking on that street every tuesday" not good?
I'm not sure that it is technically wrong, but it maybe because it is a very clumsy English sentence, "were walking" and "every Tuesday" do not sit well together in that sentence. The translation "My uncle and my aunt used to walk on that street every Tuesday" is much better.