When you are 60, do you think your sexual preferences have faded away? No, they stay there through the life.
Nothing to wonder in it.
It's not suggested to see your parents fuk any way though ..... 
yeah but... doggy I mean... a few years back my mother goes to my PC and clicks on something on the desktop - WHATS THAT ..CLICK!!!
It was a clown raping a woman doggy!!
She: Thats pretty disgusting
Me: The clown mask?
She: No the position they are using
Me: Me chuggles while turning it off - welcome to the 21 century mom (thinking - holy shit my parents got old).
Guess she was playing all alone.
Next morning breakfast after I walked in on both of them was awquard to say the least...
Me: Pop can you pass...hurrDURR... pass the butter please
Pop: Sure son
Me: Mom Pass the bread please?
She: Sure son
.........
Me: WTF I SAW YOU FUCKING YESTEREDAU!!!!!