"In Paris they simply stared when I spoke to them in French; I never did succeed in making those idiots understand their language" -Mark Twain
I´ve studied four foreign languages and the only one that wasn't a "Romance Language" was ASL or American Sign Language. It's also the only one I don't mix in with the other three.
I studied French in school for years, then I studied Portuguese for six months as we anticipated our big move to Brazil, which turned into Argentina and my ongoing study of Spanish. Each time I began a new language it was as if the other was flushed out of my mind. Sometimes though, I would slip in French or Portuguese into my communication efforts as I struggled to live in Spanish.... It was less helpful than you'd think.