I read it years ago, I remember it was old. It was about a maid who began working for a certain family with lots of brothers and sisters and she would fuck each one of them by the end of the manga. It had various chapters and each one was about one of the kids, some of them were older, maybe already adults.
It's been itching in the back of my head cause I can't remember the name. So thanks in advance!
Edit: I also remembered she had short black hair, if that helps.
Edit: I found it! It was Lovely Maid by Umino Sachi.