Incest is absolutely wrong. But feelings are just feelings. If you are living with an attractive young female, it’s not unusual or terrible for a young man to have some sexual feelings about her — even if the woman is his sister. Nature does that. But most cultures have a taboo, law, or moral code that lets everyone know it is not okay to act on it. As long as you keep those feelings to yourself and don’t in any way try to act on them, you may be able to categorize those feelings as impulses that are disturbing but not abnormal.
However you also say you are deeply in love with her. That does concern me. Love for a sister is not being “in love”. It makes me wonder whether you are having difficulty connecting with girls in general. If so, it may be that you are directing your longing for a relationship at a female who already knows you. In that sense, your feelings may be practice for when you do identify someone you would like to start seeing in a relationship.
It may also be that you are scared to try to get close to someone so you distract yourself with these thoughts about your sister. If that’s the case, the best “cure” is to start taking some risks by hanging out with a group of friends that include young women as well as young men. The only way you will meet someone to love is by being social.
If you find the sexual impulse difficult to control, please make an appointment with a counselor to talk it out. Acting on those impulses, even a little, would damage your relationships in your family for a very, very long time. Better to discuss it with someone who can help you explore what it’s about.
I wish you well.