Wow, What a favorite question of mine, your question brought a smile on my face! Saritha helped me in cycle when i was 9 and and my dad helped me learning Scooter when i was 16!
I was around 5 (definitely around 4-6). My oldest sister taught me. I still remember part of it, 15 years later. I lived in a little town and all the kids rode bikes early on because we were allowed to go pretty much anywhere on our own.