Until today 5 souls on motorbike was the most I'd seen...4 people plus a dog in the basket on the front. Never thought I would actually see more but today I overtook a woman on a bike with 4 small children plus of course.....a dog in the front basket!!
My personal favourite motorbike sighting was in Nigeria, I saw this not once but twice, a taxi bike (okada is the Nigerian term) delivering a coffin, the coffin was fastened on sideways. I'm not sure if they were occupied or not.