Is it normal that my stepbrother and want to have sex? 2 hours!!

My mom and my stepbrothers dad are both dating and have been for the past 2 years, when I was 16. We've been living with them for as long as they are dating and me and my 'brother' are always seeing them kiss and hug and stuff. We developed a bond through them kissing and we always laughed about it and I liked him. Because we live in California and we are in drought, we secretly shower together so we don't have to take a 30 second shower each.

The first time we did was a month after I moved in and I saw his whole body. Penis, abs, everything of course. he saw mine and I sorta secretly touched them while in shower. But, of course, we turned away from eachother and had normal talks. I occasionaly saw him taking a peek at my ass which is where things got weird, and I occisonaly saw him stroke his 8 inch penis. I used to get horny a lot. Then one day I saw him stroking again and giggled and he said "is it ok if I.. touch you?" and I was like "Sure" because my mom and his dad weren't home and would be gone for 3 or 4 hours. He turned around, bent down, and started to stroke and do stuff to my ass and I really liked it. I stroked his back when he did that and he quickly looked up, startled. I murmured and curled a smile and said "it's ok, do it ;)" and was enjoying it more by more. Later he got up and hugged me while wiping his penis and I saw a gigantic erection. I wiped my ass around his penis and sorta laughed and then he came close to my face and I was close to his so we kissed hardly and just shaked around like that. Then later I had to leave because I was getting so wet and horny after 5 minutes, left, put on a thong and bra.

5 minutes later I was drying my hair (still wearing my bra and thong) and I saw him looking. He was wearing brief underwear and I could see his penis bulging out but I think he was covering up. I could tell by his face he wanted to fall inside me, but he at the same time didn't. I curled up a small smile and (we were both sitting on the couch a little away from the bathroom) sat on his lap (with my thong and bra on) and just played around, pushing back to his chest. I saw him move his boxers down and his penis was wiping my ass. (We were both cleaned off and laughing at this point) This went on till we repeated the shower scenenoria and controlled ourselves so we wouldn't go crazy and reproduce or something. I just kept moving around and finding a perfect spot for his lovely dick. Then later I heard the garage door open, meaning our parents were back. I quickly put on my clothes, got up, leaned in again (With my bra touching his abs) and wrapped my arms around his neck with his around my hip and one stroking my ass and kissed him in the lips. We both wanted to do more, but we couldn't. That was all 1 hour ago. My brother and I planned to do that again during night, but I don't know. Is it ok? He's sorta my stepbrother and I don't think our parents will get married. I used to sit on his lap a lot and he got lots of erections and I loved them all, but now we're going to do real sex. We're both ready for it and he has condoms n stuff but is it ok? Is this ok? Thanks.