Is it normal to kiss your siblings on the lips?
Depends.It depends
It depends on your family and culture: some siblings share a quick, affectionate peck, while others stick to cheek kisses or hugs. What matters is that everyone involved is comfortable with it.
Families have different ideas about affection. In some, a quick kiss on the lips is an ordinary, nonsexual greeting or goodbye; in others, it feels unusual. Neither reaction is automatically wrong.
The key is comfort and consent. If a sibling doesn’t like it, respect that and choose another way to show affection—no guilt trips or pressure needed.