Meeting my sister for the first time

I meet my half sister for the first time and am pleasantly surprised.

I was born to a single mother. My dad was a short time romance and they didn't last. Mom found out she was pregnant 2 months after they broke up.
I grew up not knowing my dad or much about him. I knew his name but not much else.
When I was thirty years old, I decided to try and find my dad. I wanted to meet him and find out about him. I wasn't sure if he even knew about me. I wasn't expecting anything from him, just wanted to meet him.
It took a while but with the help of a girlfriend was able to locate him. She was better at meeting and talking to people cold than I was, so she made contact with him and told him about me. Surprisingly he was excited to meet me and wanted to know all about me. Susan, my gf made arrangements for us to meet at a restaurant in a city between where we lived. Susan told me a bit about him. Not much, because she wanted me to find out myself. But she did tell me that I had a sister and she would also be there to meet us.
I was excited but also a bit nervous. When we walked in to the restaurant I spotted him right off. He and I looked the same in the face except for our age differences. His daughter, my sister was there with him. She too looked very similar in the face as us despite having a different mother. I was struck by how beautiful she was. It was odd but I felt strangely drawn to her. I could not take my eyes off of her. I could tell she felt something about me as well.
We had a nice dinner and got to know about each other. His wife had passed, and he had raised my sister since she was 7. She was quite opinionated and not shy, unlike me. Her and my gf Susan seemed to hit it off immediately.
I found that my dad and I shared a lot of common interests and characteristics. We both had interests in mechanical things and history, were both a bit reticent. My sister was also similar to me in many ways, just more outgoing and forward.
After a bit of time, we all became quite familiar to each other and spent time together. My sister and Susan became good friends, and sis would often spend nights at our place. I often would see her in her sleepwear running around the house. I didn't know at the time but there is something called Genetic Sexual Attraction. We both definitely felt it. I often caught glimpses of her in the bedroom or bathroom, and she liked to run around the house with not much on. Susan liked to tease me about it making comments and stuff. I will admit that some very naughty thoughts were creeping into my head.
Anyhow, this went on for quite a bit. The sexual tension was definitely building. I couldn't stop thinking about my sister. The curve of her hips, flexing of her legs, bending over in front of me giving me teasing glimpses of her panty-less bottom. Susan noticed this too and began talking about things. She thought it would be hot if we got together. I began to notice the way they would talk together and giggle between themselves. Sis would often blush at something Susan would say in her ear when I was around. Sis, (Ellen) started becoming more familiar around me. At first just a touch that would linger , a hug a little firm with her pressing against me with just a t shirt on. Couple of times when we would hug I let my had brush against her ass. This made her shudder a bit and I began to wonder how far I could push things. I was struggling with my desire for her, yet I didn't want to ruin things between my gf and I, or ruin the relationship with my sister.
Long story short, I was in a state of constant arousal. I also had a very high sex drive. I was wearing Susan out. She loved the attention and loved sex, but it also led to having a lot of irritations. Rather than just cut me off we talked about it and decided to do other things like oral, anal masturbation. Found out later, Ellen and Susan were talking about it and Susan found that Ellen also had a very high sex drive. Half kidding she suggested Ellen and I should take care of each other. They talked about it and decided that Ellen would seduce me. They were both good with it.
One night we had been drinking and Susan said she was going to make a run into town and do some shopping. Said goodbye, and said "You kids be good now" and left with a big smile. I was sitting on the couch and Ellen brought out two beers for us and sat down next to me. Close enough that her leg was against mine. We both had shorts on and the warmth of her skin touching mine was wonderful. I could smell her cologne, the freshness of her hair and the subtle scent of her arousal. I had a throbbing erection and my head was spinning. She reached up and turned her face toward hers looking deep into my eyes. I could smell a slight hint of wet pussy on her fingers. We sat there staring at each other, both of us almost a mirror image of the other. Before I knew it we leaned in and began kissing. Gently at first, then becoming more fierce as our arousal rose. Her tongue pressing to mine ,our lips sealed our breath exchanging in and out until we had to come up for air. Our hands began pulling at each others clothes til we were both naked. Her breasts were perfect with a little hard cherry on the tip. She played sports so was very firm feeling even though she was a bit stocky like me. We stood up and she threw her legs around me and I cupped her firm ass cheeks, massaging them gently. I was wanting to take it slow and enjoy every bit, but she lined up my cock to her dripping pussy and drove herself onto me. Squeezing me hard with her legs with her controlling, she rode me up and down groaning and saying, "Fuck me hard and fuck me now! And don't stop even when I cum!" She began shaking and shuddering with her orgasm with her cunt walls milking me very strongly. As she wanted I kept thrusting deeply in and almost out until I came. When I came she rolled her eyes back into her head and gasped and didn't breath for a few seconds. Aftershocks rolled through us both until I felt my legs weakening and guided our entwined bodies to the couch. We collapsed and lay there together with me inside her both of us totally spent.
We slept for a while and when I went to stand our cum had dried sticking us together. As I pulled away to stand, my cock unpeeled from her pussy lips. Being still sensitive the feeling was unbelievable as our skin pulled apart. I was hard again and she grabbed me by the neck, pulled me to her and said "I need some more, honey" I entered her again and we fucked for a bit which made me cum pretty quick. I buried my cock as as I could and filled her once again.. By now I was so sensitive that even the slightest movement sent mini orgasms up and down my cock. I wanted her to cum again so I pulled out my dripping cock and went down on her sloppy cum filled pussy. I put my lips around her clitoris and began sucking on it like I was giving a blowjob on a tiny little cock. She started cumming right away and each contraction of her pussy squeezed out cum and air making pussy farts. Her little rose of an asshole was twitching too, so I stuck my tongue into it. This made her cumm even harder and made her asshole squeeze my tongue.
When we were spent again, we got up and went to the bedroom. We lay there arms and legs entwined kissing and enjoying the taste of our juices on each other and fell asleep;
Later I was awakened by Susan sliding sliding into bed putting her arms around me. She whispered into my ear "I hope you got a little left for me"