I'm in my mid-30s. It's certainly "slower" than when I learned languages in my early 20s. As for motivation, my wife is Korean and our young children speak better Korean than me already =(
It's a similar situation for me. I want to make things easier for my in-laws who strongly prefer speaking Korean at home. No kids for me yet but I plan to learn it with them someday. It's a fun experience because of how excited 장모님 is after hearing me say a single word.
