Same with me. Dad is Mexican and I took Spanish because I thought he could just help me every time I got stuck. At 15 years old it did not occur to me what a wasted opportunity it was that he never taught me.
I ended up learning Japanese later in life through tons of immersion and living in the country, and knowing what I know now I wish I could have explained how important bilingualism is to 15 year old me...or even my dad. It is the single most eye-opening thing I've ever done. Something about it just makes you so much more cognoscente about everything you say and do even in your native language. It's like I "came online" or something.
I ended up learning Japanese later in life through tons of immersion and living in the country, and knowing what I know now I wish I could have explained how important bilingualism is to 15 year old me...or even my dad. It is the single most eye-opening thing I've ever done. Something about it just makes you so much more cognoscente about everything you say and do even in your native language. It's like I "came online" or something.