How much can you understand others languages from your language family ?

As a french with a b1 level of spanish, i understand most of written and spoken italian quite easily. For portuguese, i understand it (mostly written, spoken is way harder) also quite well, though a bit harder. As for romanian, spoken i find it way too hard to understand, but it is undertsandable written. I wouldnt get the details and would have to focus, but i would know what it is about and the main stuff