Gunko being a natural born CD makes no sense tbh. How did Brook serve her then? Did her parents leave the Holy Land like Homing?
We still have no idea of her backstory
1. she could have been forcefully brought into the CD family as a Maymar from the lower world. Hence why she forgot her memories
2. Brook served the CDs at one point in his life. Not the first time we got a SH with a shameful past aka Prince Vinsmoke
3. Maybe she wanted to go with Brook into the lower world but her CD family forbade it and erased those memories of her with him
Oda will explain in due time this is Brook story after all. Either way Gunko is at the center of this and Oda def putting more care and thought into her backstory than Kaido Fujitora and GB that’s for sure