Could someone explain me the use of de.... el... in this sentence?
"el" is used when you are selecting elements from a set. It literally translates as "from/out of", like the word "ex" in Latin.
The sentence "unu el viaj gepatroj" means "one (out) of (the set of) your parents", or more casually, "one of your parents".
I've been trying to stay away from the comments for a while, but I'd like a little refresher about what each "of" means. ("da, de,& el")
Ĉu mia onklino ankaŭ povas esti la edzino de la frato de unu el miaj gepatroj?