It’s very unlikely that a frum person who got married in 1770 and had ten children like Meyer Amschel Rothschild did has no frum descendants at all but from his five sons who went into banking it is safe to say that none of their descendants are frum. Therefore if he has he has frum descendants they would be from his other five children who have no money .
Of interesting note the only major Rothschild scion to have been killed by the Nazis during the holocaust for being Jewish wasn’t actually Jewish. Élisabeth de Rothschild was a Catholic woman who married Philippe de Rothschild. (she officially converted)