Their family make billions by tricking the public, and zigging when the public is zagging.
After the battle of waterloo, they knew Napoleon won but they tricked the town in France with a fake messenger saying Napoleon had lost. The price of gold crashed as everyone freaked out. Then the real news came the next day, and they turned around and sold all the gold and made over 10x their net worth in 1 day.
This was in 1815. Soon after in the 1820s, they began doing central banking loans to many European governments and nobility, using this money to loan out.