New Kids on the Block: Good Genes or Good Docs?

New Kids on the Block have got the right stuff.

Here's Danny Wood, Joey McIntyre, Donnie Wahlberg, Jordan Knight and Jonathan Knight during their boy band heyday in 1989 (top) -- and 24 years later, Joey, 40, Danny, 43, Donnie, 43, Jordan, 42, and Jonathan, 44, in NYC recently (bottom).

They're hanging tough.