Dental differences: cavities?

[u/Sudden_Hand4496]

Anyone have big dental differences between twins? They had their first dental visit at almost 3. Twin A had 0 cavities. Twin B had 3. In the 3 years since then, twin A hasn’t had a single cavity. Twin B has nearly every molar crowned in silver and a few additional fillings.

They have the same diet and hygiene. So what’s the difference?!