My kids all went to Welsh-medium schools and all speak Welsh. It was my ex-wife's first language. I tried my best to learn, I even went to lessons, but I just couldn't get my head round it. I can understand a lot, and can read a bit, but that's about it.
Language is taught differently these days. I had French for just one year in school, but fifty years later, I can still use it to make myself understood. We learnt verbs 'parrot fashion' back then, and I've never forgotten them.