Hello Bernat

You need to be in Spain at least for 6 months ( 180 days ) every year. If you cannot meet that requirement due to exceptional reasons, as looking after a relative may be, you need to show documented evidence when filing the renewal application, such as medical reports and birth certificate to prove the family relationship. Each case is different. I would recommend you to ask an immigration law expert to examine the documentation that will justify the absence before you file the application.

Regards,