There's another killing of an uncle by a nephew in the early episodes, but I won't post it here because it's one of the rare spoilers in Columbo ;-)

A couple of additions from the later episodes:

A brother killed a brother in "Strange Bedfellows"
An uncle killed a nephew in "Death hits the jackpot"

Like a lot of you, I've never managed to really get "into" the later version. But JACKPOT is one of the exceptions for me, so I'm sorry I didn't think of it.

It took me a while to realize which episode of the FIRST version you meant, but now I see what you mean.

I don't know about the later version, but when it comes to the first series, there seems to be only one murder of a mother-in-law. Which is interesting, considering all the traditional jokes about that particular kind of murder!

Is there another uncle murdered? Or T'ISN'T there?