How Many Khans Could There Be?

From abc13.com (of Houston, Tex.):

Candidates with same name cause confusion

(11/1/05 - KTRK/HOUSTON) - When Houstonians head to the polls next week they'd better take a good look at who they're voting for in one Houston city council race.

The race for city council district F may be confusing. The main challenger for incumbent MJ Khan is a candidate named KA Khan.

[snip]

"For the longest time, I thought they were related," admitted voter Laura Walpole. "I thought they were father and son, because the last name is spelled the same way."

[snip]

[Read the whole story]

Genghis Khan is credited with 16 million direct male descendants, and the Khan surname is ubiquitous in Central Asia. What are the chances that two of that name would settle in Houston?