Mr Whelan was born in Canada to British parents but moved to the US as a child. He is currently director of global security for Michigan-based automotive components supplier BorgWarner.
He is a citizen of four countries – the US, the UK, Canada, and the Irish Republic.
Mr Whelan joined the Marine Reserves in 1994 and rose to the rank of staff sergeant in 2004. He served in Iraq for several months in 2004 and 2006.
He was convicted in a 2008 court martial on charges related to larceny and received a bad-conduct discharge. Details of the charges have not been made public.