Recently bought Diablo 3 (digital) for switch and added it to both consoles.

Want to play with my son and he has a children's account under my parent account. When we are both online (bethsda online or whatever it is called) I don't see him and he doesn't see me.

I don't have any one else in my friend's list (sad I know) and Nintendo Online notifies us when the other one signs in so the Switches recognize that we are both online. But Diablo network doesn't seem to recognize that we are both online. Why can't we connect to play together?

***I have an individual Nintendo Online plan not a family account, but I was told you didn't need an Nintendo Online subscription to play together online if you were on wifi.