A posthumous birth is when a baby is born after their biological parent has died. That means the mommy or daddy who made the baby inside their body is no longer alive when the baby comes out.
There are different ways this can happen. Sometimes, the mommy or daddy leaves behind eggs or sperm that can be used to make a baby even after they're gone. Other times, a baby is already growing inside the mommy's belly when the mommy or daddy dies.
When this happens, it can be very special but also very sad. The baby might never get to meet their biological parent, but they can still learn about and love them. The people who are raising the baby, like grandparents or other family members, will do their best to give them a happy and healthy life.