I've wanked while wearing my dads undies a few times when I was 16ish. I wasn't attracted to my dad but sexually curious. One day I found he left the bathroom door open a crack accidentally and I hid in the room next to it and watched him shower with his cock bouncing as he scrubbed himself over. I started to strategise after that, pulling his undies under the door and placing them back on his bed so he'd think he forgot them but those were failed attempts. Saw him shower naked a few times, was satisfied with that and my curiosity moved on to watching the neighbors.