He was born on 25 October 1809 as the fourth child of Francis Smets and Marie Agnés Abeels in Gotem, Belgium, and he married Johanna Maria Buteneels in Berlingen on 27 April 1832.

[1] Smets and Buteneels had three children together: Jean Thèodore (1836–after 1863), Jacques (1840–1916), and Catherine Elizabeth (1843–1890).

[1] During the time he named Aachenosaurus, Smets worked at the Collège Saint-Joseph in Hasselt,[3] and a rumor abounded that he completely withdrew from science out of pure embarrassment after 1888, but not until he had published a paper on turtles in 1889; this rumour was later proven false.

[3] Based on these fragments he determined that the specimen was a hadrosaur reaching an estimated 4-5 meters in length which might have had dermal spines.

[3] He defended this conclusion, citing that the fossils had been examined visually with the naked eye, magnifying lenses and with the microscope.