The modern language, which is having a significant revival since the last census of 2011, will certainly show some signs of influence from those sources, but it’s one of the oldest languages in Europe and is definitely separate from them.
It’s part of the Celtic language family and traces its roots back to proto Indo-European.
Jennifer Paxton’s The Celtic World is a good historical overview of Celtic history and includes some material on the language families and how they evolved. You may be able to check it out from your local library.
If you’re curious to try it out, Duolingo has some solid materials as does Say Something in Welsh. It’s amazing how much I’ve been able to soak up in a month or two without working at it very hard.