"Din søn er kun en dreng."

Translation: Your son is only a boy.

[Isaac_Luna_]

when would you use "kun" instead of "bare"?

[Marinia]

kun means only and bare means just. In many cases you can say both things, like in English you can say only a boy or just a boy. Likewise you can say kun en dreng and bare en dreng. Just depends on what you wanna express with it.

[r0ckyq3en]

no no no no nooo your son can be nonbinary, a female, stay a male, and MANY MANY more things.