For me it was a very sudden realization. I started out as the spanker with my first girlfriend, She would get over my knee and I would hand spank her bare fanny and finger her clitoris at the same time.
After we broke up and I started dating the woman would eventually become my wife.
I waited until we started having regular intercourse to suggest spanking with her. I said " would you like to try spanking?" Her response was "YES!! " but she added that she wanted to wait until she and her sister moved into their new apartment.
When the time finally arrived I got the surprise of my life. I made a move to give her a spanking and she stopped me immediately and said:
Hold it mister I'm not the one who is going to get spanked in this relationship.
She called me over to her, spread her legs and told me to go down on her. I was wild with passion and down I went.