the baby is ikurou the boy is norihiko http://www.mangago.zone/read-manga/tourou_no_ori/mf/324040/Ch2/pg-4/
bottom right of page tells you that.
I'm pretty sure it's Ranzou and Ikurou when they were children, presumably at a time when Ranzou's hair was still black (notice the lighter eye color) and before his father had imprisoned him. Newest chapter Norihiko is shown to be too old to be that child. He was already a young adult at that time having lots of fun tunnel exploring the boy's mom.
Maybe the boy is Ranzou Thanks for explaining (^_^)
Please tell me who is this baby and the boy.
http://www.mangago.zone/read-manga/tourou_no_ori/mf/324040/Ch2/pg-2/