This is usually quite normal and is due to an hormonal effect during pregnancy. It has normally disappeared by this age and for this reason and seeing her sister is not affected it would be best to ask your paediatrician to see her.
The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal
advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.