My Horny Sister

I'm the eldest of 2 and have my own apartment albeit owned by my employer. So, when my sister came to the city looking for work, she decided to stay with me. Nothing much happened at first, my sister is a very self-assured type. Also not bad looking, I'd been away on a job and returned early one afternoon. Thinking my sister would be at her job, I went to the apartment to put away my suitcase and relax after a taxing trip. Unknown to me my sister's employers had a small fire and was closed for renovations (2days). Mainly to rewire and to remove the smoke smell (my sister told me later). I walked in and caught my sister naked and masturbating herself on the lounge, both shocked at first. But we recovered fairly quickly, and my sister noticed the bulge in my pants. She asked me to show her my hard-on as I'd seen her, I decided why not and dropped my pants and shorts. Her expression changed and she got even more excited on seeing my hard cock. She straight out asked me to fuck her as she was extremely horny herself, from lack of sex since moving to the city. Only offers of dates she was from the creeps as she referred to them. I myself was between girlfriends after separating 2 weeks before and was away for most that time. So, with my sister willing and I already had a hard cock I agreed. She and I slept together for about a month before us both found new partners. But we still do sleep together every now and then, especially on rainy days and nights and our partners are away or working.