What happened to the third iteration of Yuki?
In episode 26 from around 17:25 third world and all the diary holder are shown one by one. Everybody are living happy life. At19:50 Yuno is shown with her friend in some restaurant and she sees Yukiteru outside with his family and the girl Moe Wakaba. He is the 3rd universe Yuki. Looking from those clip, Yuki is happy with his family and Moe Wakaba.

Here is the YouTube video.