My new born twin baby having jaundice.

Jaundice is a natural and normal phenomenon in all newborn babies. It's only when its level reaches a specific value that it can cause brain damage; it needs to be treated. This safe limit depends on certain factors like age of the baby, gestation age (whether the baby was born on the due date or before that). The doctor must have kept that baby under phototherapy (blue lights) who's bilirubin is in phototherapy range and would have sent that baby home who's bilirubin is within normal range. Keep this baby well fed (give breastfeeding every 2-3 hourly including night time), nothing more needs to be done. Bilirubin will go down by itself as baby gets mature. Stay in follow up, if you feel baby is quite yellow, consult with your doctor.