So, I had a thought right before going to sleep (of course) the other night, but I don't have my Wingfeather books with me to fact-check, so it's been in the back of my mind ever since.
Am I correct to say that Davion is a third child, with Illia being the first, and Jru being the second? (I believe Davion was the second born of the twins, and it is said that Leeli is the first Song Maiden Anniera has had in a very long time. Jru was made king as a result of Davion's "death", so Illia must have been older or else she would have been made queen.) (There is canonical support for her right? I'm just severely doubting myself right now 😅.) Anyway, if so, Davion would have been a Song Master.
That would explain his ease of communication with Leeli when she played music that triggered the Jewels' connection. While the siblings could see each other sometimes, it seemed like it was hard to speak to each other through the connection. Davion doesn't seem to have any problem getting speech across. His position as a Song Master would also be fitting with his use of the song of stones to meld his armies.
Maybe this is old information, but my 12am brain needs to know 😅😂.
I think Davion is the second born! In TWATWK, with the bits from the Annierad, Bonifer described the first child as twisted and deformed, and the one that came out next was perfectly normal. So, Jru would have been Song Master, and Davion is the rightful king! Hope this helps!