"We zien hem twee keer per jaar."
Translation:We see him twice a year.
In many other languages the word to cite the frequency of an action/event, differs from "time".
For instance, in Turkish we got the word "kere" that refers to "keer" in Dutch -a surprising coincidence, I believe. And we have a different word for time: "zaman". While Two is "İki", one would never say "iki zaman". It's completely wrong and awkward. "İki kere" would it be... "İki kez", "İki sefer" being the alternatives.
The same goes for Kurdish. Time is "Dem" in Kurdish. Two is "Dû". -an makes it plural. However, "Dû deman" would sound awkward. There's a match for "keer" which is "car". "Dû caran" would be the translation then.
Note that Kurdish is from the same language family as English. The similarities you encounter here are no coincidences unlike with Turkish.
One last example; "deux fois" in French. Fois doesn't mean time (le têmps), it just refers to the frequency.
The list goes on... Don't know why English has no such seperation.
With amounts so grams/liters/times/meters etc. the singular form is used so gram/liter/keer/meter even when the amount is larger than 1.
Only when you want to explicitly emphasise it the plural would be used or if there is a adjective before the amount e.g., tien verschillende keren.
So unlike English where it's normal to say two times, in Dutch it's normal to say twee keer.
Does this mean that twee keren is wrong? I suppose you could come up with a context in which it isn't wrong, though in all fairness there isn't really anything in this context that would warrant the use of keren.