16yo step daughter

Recently, I got re married and my new wife has a 16 year old daughter, so shes now my step daughter.
I've been living with them for 3 years now, and since my stepdaughter)recently started hitting puberty and her boobs have gotten larger, and late at night when my wife is working, I sometimes hear her moan from her bedroom when she’s masturbating.
When I hear her sexy moan I start to stroke myself, and get really horny.
One night when my wife was at work and I heard her moaning, I quietly got up and snuck into her room. The door wasn't closed all the way and so I saw she had a vibrator in her hand, and she was moving it around on the top of her vagina.
I got really horny, I grabbed my dick and I started stroking myself. She stuck the vibrator into her vagina and screamed a little, then moaned. I got super horny, and left before anything happened so I could jerk off.
Then, one night when my wife was at work, I was lying in bed until I heard the door open. My Stepdaughter walked in with nothing but a bra and knickers on coming forward towards me.
I looked at her and she asked if she could sleep with me as she had a bad dream. I nodded and she hopped into the bed. I said goodnight, then when I was trying to sleep I felt her ass on my legs and I went hard. She felt it because her hand grabbed my dick and she started stroking it.
I moaned a little then she got up put the light on and jerked me till I came.