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"All in all, we have four Challenger astronauts who looked somewhat like persons with similar names who are living today, two Challenger astronauts who looked like their siblings, and one Challenger astronaut who apparently didn't look like anyone else bearing the same name. This conspiracy rumor about still-living "dead" Challenger astronauts is some good tongue-in-cheek fun, but as an actual theory it's sorely lacking in evidence and cohesiveness."
http://www.snopes.com/politics/conspiracy/challenger.asp

Similar names you say! In some cases identical first and second name, what are the odds.

Well some of them are siblings, so it's not surprising they both look similar and share the same second name.