Errors in writing, voluntary changes by the bearers, modifications for language reasons... There are many reasons why the surname Siliwangii may have undergone changes or modifications, and from those modifications, surnames similar to Siliwangii may have appeared, as we can see.
Discerning whether the surname Siliwangii or any of the surnames similar to Siliwangii came first is not always easy. There are many reasons that could have led to the surname Siliwangii being written or pronounced differently, giving rise to a new, different surname Siliwangii with a common root.