It's just me and my dad so we are naked most of the time, except during the winter. He always said that there was no problem in being naked as long it was just the two of us in the house, but I only started to get fully naked after the pandemic started.
The first time he saw my erection I had just woke up and went to the bathroom, cause I didn't want him to see it, but he was already there (there is only one bathroom in our apartment). He said I had nothing to be ashamed and continued to brush his teeth, my hard on died right after. After that I got less concerned if he saw it or not, sometimes even after I jerked off I would go out of my room with my dick flaccid hanging around.
One day I ended up seeing him hard for the first time , it turned out his dick was thicker, but mine was bigger. My dick is 19 cm, my dad is 17 and a few centimeters. I actually bothered to ask him and he answered with no problem.