I think the answer to this questions depends on the person's native language and interests. I, for example, speak both English and Spanish, so it was relatively easy to learn Italian and Portuguese because they are both derived from Latin, like Spanish. :) Also, if you are interested in a particular, culture or country, you might find it easier to learn the language associated with it.

I couldn't agree more with what Sandrah said.

Example, In my case; My native language is Danish which is very closely related to Norwegian and Swedish. So even though I'D NEVER STUDIED neither of those languages,I still understand about 80% of what they're saying when I speak with my Norweigan/Swedish family, when we visit them every 6months.

and just to point out how related they really are and it's not just me who is good at it;

My parents watched Norwegian and Swedish cartoons as kids, but since then. They haven't watched any Norwegian or Swedish television. They understand and speak fluent Norwegian/Swedish.

I agree with Sandrah.