Should I learn language X first if it will make it easier to learn language Y?

This is a common question, but the more you think about it, the less sense it makes. The fastest way to learn language Y is to spend the available time you have actually learning language Y instead of learning a related language that will require you to learn a lot of things that are not useful to learn language Y. Learning a language takes a long time, and if you are not interested in language X itself, you are more likely to feel discouraged and give up and never even get to learn language Y.