Oda is known for pulling the bait and switch when it comes to introducing characters, and when you do it with Buckingham Stussy and Whitebeard you get the saddest love story in all of OP. We don’t even have to overcomplicate things.

The past

Whitebeard loved Stussy and despite her not being an official part of the Rocks Pirates and not liking him , she eventually concedes and becomes one of the crews Freeloaders.

All Whitebeard wants is a family with Stussy and eventually he gets it and they have a son.

Whitebeard promises a good future leaving a “fortune” behind for his “family”. But his son dies, him and Stussy split up , Rocks Pirates gets disbanded.

The Present

Whitebeard never recovered from his lost family and son, and creates a crew where everyone is called his son no matter their gender; and made that new crew his family.

Stussy being the freeloader of MADS and not contributing much; also has no money so she struggles to produce a viable clone the same way Vegapunk and Judge can, hence Weevil being defective. Weevil is also a clone of Whitebeard or their deceased son.

Stussy for whatever reason is unable to connect with Whitebeard before his death and values money so much because as Vegapunk explains, it’s the basis for all science, and she had to use science to get the only family she has.

Stussy is now defending the legacy of the man she loved all the while looking for the “fortune” he promised his family. Stussy’s introduction quote Becomes a lot more meaningful when you realize what money means to Stussy.

“Silly boy… What’s the use in revenge?! It won’t get you a single belly! Money’s what matters!”. Replace money with family and it sounds a lot like Whitebeard.

Theory by KingSimp_Son (https://www.reddit.com/user/KingSimp_Son)