They are literal children though.
Weevil is simply "stupid", even though that isn't even the term, he is just simple minded and comical.
I know, the idea is that He looks like a Stupid Adult,
But i believe there are enough Hints for me to theorize that He is indeed a Kid just like Momo/Bonney,
His Unusual Body + His Mother being a Scientist + Being "Self-Proclaimed" Family of WB + He wasn't Mentioned before ... etc
Clearly suggest that Oda wants us to be Suspicious about this guy,
Initially i thought that WB & BM (Original Emperors) are like Father & Mother of Pirates, They clearly represent Odin & Frigg imo,
Then We have Kaidou who was like Baldr of Pirates, while Shanks is Tyr ... etc
So i wondered who is Weevil? He is clearly Someone driven by Vengeance, and i wondered why He only appeared recently after WB's Death, and why He has such a Childish Mind despite his Mature/Adult Body, so i searched if there is a Norse God that matches this Description & there is indeed One,
Vali is Son of Odin who was born for Vengeance, and it is said that He grew up to Adulthood in a Single Day,
I think Bakkin somehow made her Son grow super rapidly, hence why He is Stupid despite being Old,
His Animal is also a Beetle, and other guy who has such Theme is Heracles (Usopp's Teacher) and what did He teach Usopp? He gave him Pop Green that are Plants able to grow from seeds to full-size in moments, so i don't think this is a Coincidence