I don't know who "their" is referring to, but read, read, read, and let us know what you discover.
http://millercenter.org/president/fillmore
http://en.wikipedia.org/wiki/Millard_Fillmore
http://www.whitehouse.gov/about/presidents/millardfillmore
http://www.millardfillmore.org/
http://www.history.com/topics/millard-fillmore
Were there any key events in Millard Fillmore's life that shaped their dream for the United States?
2 answers
Um that's a stupid answer. The person literally said 'Millard. Fillmore'. That's who 'their' is referring to...