How did the gang hear about the passing of Bowser's wife? How did his parents react to the news?
It was kingdom-wide news; normally the laying of an egg to the next royal heir is of course a big deal but the parents would at least be given a few days before the news is broadcasted to have some privacy. Not so much with Bowser’s wife; when she had complications it was immediately broadcasted, and mere hours after she passed on the whole world knew that she died. Unfortunately that’s how the gang found out; Bowser wasn’t really given much time to do it himself since the window to do so was pretty to begin with.
Bowser’s friends reacted by immediately coming to visit him; honestly it’s safe to say a good chunk of each kingdom did. The queen of Koopa Kingdom was beloved and in good standing with everyone, so the world felt the vacancy she left; her funeral was huge and had many attend. When the main funeral passed, Bowser’s friends held a much more private one for his sake, something he very much appreciated; despite the good-will and peace this world has I’d imagine paparazzi may still be an issue, so it’s hard to get a bit of privacy to properly grieve with cameras in his face.
Bowser’s parents reacted much the same way and, in one of the few times they actually acted with some moderate decorum, tried comforting their son, going so far to shoo away film crews and reporters when they tried to interview Bowser immediately after the wake. They enjoyed the queen’s company too so they were honestly sad to see her gone. This does lead to a problem later though, when Bowser starts dating Luigi. They aren’t nearly as approving of his choice of partner then, but that’s something I can talk about in detail later. o3o