Robert Dundas, the 2nd Lord Arniston, was probably born between 1642 and mid-1650s. He was the son of Sir James Dundas, the 1st Lord Arniston (born around 1619, died 1679).
He was educated abroad, and was a supporter of William of Orange.
References:
http://www.historic-scotland.gov.uk/index/heritage/gardens/gardenssearchsummary.htm?s=Arniston&r=&bool=1&PageID=2309 [accessed 7 April 2008]
J. M. Rigg, ‘Dundas, Robert, Lord Arniston (d. 1726)', rev. Anita McConnell, Oxford Dictionary of National Biography, Oxford University Press, 2004 [http://www.oxforddnb.com/view/article/8256, accessed 7 April 2008]