What if your niece has a baby what relationship is the baby to your child?

Great niece's baby is your great-great niece or great-great nephew.

The system works like this:

• Your niece's child is your great niece/nephew
• Your great niece's child is your great great niece/nephew
• Your great great niece's child is your great great great niece/nephew
• Your great great great niece's child is your great great great great niece/nephew...