I used to work at a nursing home. A lady whose first language is Spanish literally laughed at me when I used the word "marido.". She was from Mexico, and I wonder if marido is used more frequently elsewhere.
Big brother could just be a description, i.e. that he is large. Big how you use it is usually accepted as an older brother - you often hear it more in American English, but not exclusively - but this is trying to get the correct translation.
I had the correct answer above and it was flagged as incorrect. Also took a heart away. Duo makes mistakes too. It forced me to repeat part 1 of a short story that I had read and completed. Wasting my time.