Is it normal to kiss your sister?
Depends.It depends
A quick kiss on the cheek or forehead can be normal family affection, though it depends on your family and culture. What matters is that you’re both comfortable with it and that it isn’t romantic or sexual.
Families have different habits: some siblings kiss on the cheek or forehead as a casual hello or goodbye, while others never do. A kiss on the lips can feel more intimate, so people’s comfort levels vary even there.
The key is mutual comfort and clear boundaries. If either of you feels awkward or doesn’t want it, don’t push it; affection doesn’t have to involve kissing.