In the third opening of Attack on Titan we see a man and a baby holding hands. Does anyone know who these two people are? I can't remember seeing them in the manga.
This scene is depicted from Shingeki no Kyojin manga chapter 86, "That Day".
Grisha Yeager and Dina Fritz got married during the rise of Eldia and had a baby. This baby was named Zeke, which further betrayed whole Eldia and joined the Marley Forces.
Probably this is not totally explicit, but, according to this Website (and many others): http://aminoapps.com/page/shonen-amino/4316391/alerta-spoiler-primera-parte
These are hands from Grisha and Zeke.
This is the hand of Eren Yeager and his son/daughter with Historia Reiss/Fritz, could be Historia Yeager in the future. Though this theory cannot still be supported yet by the manga, but I assume that this is where it leads, the future, based on what the manga is currently potraying.