Refer to the input text as context and select the correct relationship between 'St George Bank' and 'Westpac' from the available options.
Options: location of formation, parent organization, stock exchange, position held

Mrs Kelly was chief executive and managing director of St George Bank from 2002 to 2007 and CEO of Westpac from 2008 until early this year, overseeing a merger of the two banks in 2008.
parent organization