I had never in my life heard of the Dutch duo of this year, whose names I actually will have to Google if I want to incorporate them into this answer I feel like the girl is....Mia? Nia? No idea about the guy.
In 2018 we had Waylon and in 2015 Trijntje Oosterhuis. Can't say they're superstars, but at least they were pretty well known (especially Waylon) Anouk in 2013 was the only time I remember we really had a big name with a well-known career participating.
Edit: of course there was 2014 with The Common Linnets, who were not at all a known duo, but individually Waylon and especially Ilse DeLange were definitely well known.