Well to be honest I lived in South Jersey for five years and I've learned that in that kinda area with a similar onset of dense population in NYC it is very much possible to have many people with the same name. However even though I'm sure there were multiple Andrew Klein I'm not entirely convinced it's plausible for two in such close age to be living at the same a dress. It could be possible they were multiple entries? If they were on the same day then perhaps it was filled out wrong and instead of throwing it away they accidentally registered it or maybe He had a cousin roughly the same age living with him. Have you checked the 1860 Census by chance? Maybe they will have some answers if there were two living at the same residence.