Though many people use "different than," only "different from" is logical.
Notice that, in math, the difference between two numbers is basically the distance from one to the other.
Also, we say, "a differs from b."
So, "different from" makes complete sense, and "different than" has no logical basis, except in the following type of context:
These two people are more different than these other two people.
In that context, we have a "more ... that" construction with "different" between "more" and "than." So, "than" is working with "more" rather than with "different."
"Than" works with words that qualify, such as "more," "bigger," or "easier."
"Different" does not qualify. So, it doesn't make sense to use "than" with "different."