I don't think anyone in Sanas family would have gone to Yousef and told him to back off from Sana, she's not related to Caroline Bingley. He could have overheard her mom saying something to her dad or Elias, tho, like "I'm worried about S spending time with Y"/"S said she likes this muslim boy the other day, do you think it's Y or someone else?"
that sounds VERy plausible !! but im sure no one intentionally ruined it between them.
but i also think yousef’s explanation and reasoning wont be too groundbreaking, it could be more internal. like she gave all these signs that she doesn’t want him and he decided to give up bc he ‘realized’ she didn’t like him..