It Wasn't What it looked like

I am a chiropractor, I have two step daughters and no I haven't done anything inappropriate, the youngest came in to our bedroom in the morning while my wife was showering complaining about her back I asked her what the problem was,
I knew it was just a strain, I offered to work on it and told her to lie in the floor a solid surface was necessary
she lay down and pulled her nightie all the way up I was surprised she didn't have any knickers on I wasn't complaining she had the most perfect arse, I said Ann you are naked she said its ok your my step dad, ok I said as long as you don't mind, it wasn't unusual for some woman to strip naked in my practice, I started to massage her back, I couldn't help but get an erection as I was massaging her, her buttocks kept opening I could see he anus and vagina to be honest I was having a good look, bottoms are my turn on, my erection was poking out of the opening in my pyjama bottoms I was on her left her head was turned to the right so she couldn't see my hard cock,
I herd my wife shout what the fuck are you to up to, Ann jumped a bit and turned around she looked at my hard cock and at her mother, we were pleading our innocence, finally she accepted there was nothing in it, after I explained I couldn't help getting an erection she agreed, after a my stepdaughter and her sister kept smiling and grinning at me and said there backs might be bad tomorrow afternoon, I am off that day