Take context from the input text and decide on the accurate relationship between 'Xstrata' and 'Glencore' from the options provided.
Options: owner of, currency, operator, owned by

Klein brokered the talks between the bosses of Glencore Plc and Xstrata Plc that led to the $29 billion all-share takeover of the mining group by the commodity trader in 2013.
owned by