Is it the same baby?

I interpreted the ending to mean that big brother doggy let Yeseo “go first”, and that he would arrive later as the younger brother instead. I thought it was pretty clear that that little boy is the same baby, right?

But some of the comments make me think it might not be the same person… bc she mentioned playing “another doggy” that looks just like the first…

Yes, I know I am getting too into this but I really need to know for my own peace of mind