juan es el__ de lucía. \nhermana \nhermano \nesposo \nhijo

Brief Explanations:

In Spanish, "hermana" means sister (feminine), "hermano" means brother (masculine), "esposo" means husband, and "hijo" means son. Since "Juan" is a male name, "hermana" (feminine) is incorrect. From the family - tree context (assuming typical family - tree relationships), if we consider the most likely relationship among the given options for a male - named person in a family - tree - related fill - in - the - blank (without more specific family - tree details but based on gender and common family terms), "hermano" (brother) is a reasonable choice as it is a gender - appropriate family term.

Answer:

hermano