Haven't read other replies.
Since when does getting bucked off and laughing about it = able to train a horse? REALLY!?
I've started many greenies and babies over the years, bucked off and come off more times than I can count. I'm not saying I'm downright amazing by any means, but I've been there done that. I wound up in a complete freak accident off my dead quiet mare - I broke my back in two places, slipped disc, sprained neck, nasty concussion and permanent hearing loss. This was ~4 years ago. I STILL suffer the effects of that accident every single day. NOTHING I could have done would have changed the outcome of that accident. It wasn't my fault, nor was it my mares fault. We were walking when it happened.
Bottom line - it doesn't matter how experienced you are, accidents will happen. You can do everything right and it can still so easily happen. The effects of that are permanent. Your brother falling off and laughing mean squat.
I also hope you know that bucking doesn't in any way = green.