The main Romance languages are:
They share a large common vocabulary and similar grammatical structures such that fluency in one allows you to quickly learn another. By some estimates, you can learn a second romance language in half the time you learned the first. In general, the more Romance languages you learn, the easier it should be to learn subsequent romance languages. As Barry Farber says in How To Learn Any Language:
You learn so much Italian when you learn Spanish that it’s a shame not to switch over and pursue Italian once your Spanish is adequate. Portuguese isn’t far behind, and even French, the Romance language least like the others, has enough similar grammatical features and vocabulary to help you conquer all of the other Romance languages.