It is a common condition among newborn and your cousin shouldn’t be too worried. Common treatments include more frequent feedings of breast milk, or phototherapy. If high level persists, go back to the hospital for more phototherapy treatments. In the meantime, she can continue to breastfeed your nephew. Here’s an article on the different types of jaundice: http://kidshealth.org/parent/pregnancy_center/newborn_care/jaundice.html#
Quite common especially if baby's blood group is different from mother. Have to monitor and check on his liver just to ensure nothing goes wrong. During this period, try to avoid or rather cut down on ginger intake. Old wives tale is to get some herbs to bath the baby and put it underneath his pillow. Well, i did this too.