Cruz was born a U.S. citizen since his mother was an American living in Canada. The U.S. Constitution requires a candidate for president be a "natural born citizen." Most experts believe Cruz is a natural born citizen, but no president has ever been born outside the U.S.
But Trump and others have raised questions about the legal issue and Trump has tweaked Cruz over it on the campaign trail. Not mincing words, Trump referred to Cruz as a "Canadian anchor baby" during a town hall in New Hampshire.
Cruz's father, Rafael, was born in Cuba, emigrated and married an American from Delaware, Eleanor. While Rafael Cruz is today known for his religious beliefs and sometimes controversial statements, back then he was a successful oilman. The two were steeped in the Canadian oil industry of the early 1970s when she gave birth to a son, Rafael Edward (Ted) Cruz.
Rafael and Eleanor were, to those who knew them at the time, smart and successful.
A geophysicist who worked with both of them says they were ahead of their time.
"He was a very clever man," Easton Wren said of Rafael Benvenido Cruz. "He had lots of charisma and the combination of technical capability with the charismatic personality enabled him to do well in the business here."
Wren says Rafael Cruz was the "center of the group; he would always take the floor" whenever the tight knit group of oil industry support groups would gather for a convention or a party.
Cruz ran a company called R.B. Cruz and Associates, which provided computer-driven seismic maps to the oil industry, which the big oil firms would buy and then use to begin to drill.
But suddenly, four years after their arrival in Canada and four years after the birth of Rafael Edward Cruz, the bottom fell out of the oil business and they left.
Rafael Senior became an evangelist in Texas. His son, who changed his name to Ted when he was 13, became a Republican senator and presidential candidate.
The backstory is fascinating and you can watch Drew Griffin's video report, above, to learn more.