Table top

Nice, too funny about the twins (you may not think so), they were just trying to make the top look the same age as the frame

What kind of joinery on the frame?

A very pretty top and yes, the round over was a good decision, more for looks than fragility. A big chunk of walnut is always a beautiful thing.
Wondering about the exploding glass top? You've already mentioned the twins technique. Bet they were disappointed about the new one not responding in the same way.

Joinery on the frame is of "industrial kind", i.e. in each leg there is a plywood in the middle, and solid wood on both sides of the plywood. This "sandwich" has just been cut to the boomerang-profile, and then rounded to the final form. The lower "table" is attached with hardware to these legs.

Re vipond's question about the self-exploding glass: I have my own doubts as well, and my prime suspect is our 5-year old. However, he has been able to produce an eyewitness, who swears he was at least 5 meters from the crime scene at the time of the incident. As the eyewitness is his mother, I'm not convinced but until I manage to break the alibi, lets call the explosion "self-induced"...