No they were not parent. Gran helped Nana to keep her son safe from bad things because of Nana were holder of OFA. If she kept her son with her then villians will target him to get her.
I already know all of that.
Until horikoshi confirms or denies it, it’s all up in the air. I still think he might be the father.
I am confused about that too. In the portuguese translation is saying "We" as well, so I came here to see if it's a translate mistake. His words make it looks like he was part of the decision-making. It could be encouraging her to give Kotaro or being the father himself. I don't remember she mentioning the child's father, but I saw some people saying he died. Honestly, I'll try to read it all again. (I hope it's understandable. English it's not my first language.)
Was Gran Torino the father??? When he looked back he said “they” made the wrong decision.