Who are the real wealthiest families of the world?

The Forbes list always seems to be fairly off, listing mostly publicly known assets from an American perspective. Europe has much more “old money.” What families are fairly known to probably be among the wealthiest in the world (other than the commonly named branches of the House of Rothschild). Surely various aristocratic families have accrued interest over centuries, and possibly even have their own gold reserves? It is also rumored certain Russian mafia or industrialists have become among the wealthiest in the world, as well as Arab oil families. Any information?