Breakdown of Wen ich kenne, den lasse ich immer herein.
ich
I
immer
always
kennen
to know (somebody/something)
wen
whom (accusative)
Questions & Answers about Wen ich kenne, den lasse ich immer herein.
Why does this sentence start with Wen instead of Wer?
Wen means "who" or "whomever" in the accusative case. It is accusative here because it acts as the direct object of the verb kenne (to know). Because you are knowing someone, that person takes the accusative case.
What is the purpose of den in the middle of the sentence?
den is a demonstrative pronoun (meaning "that person" or "him") referring back to Wen. When a free relative clause comes first, German often uses a pointer word like der, den, or dem at the start of the main clause to smoothly pick up the reference. It is den (accusative) because it is the direct object of hereinlassen (I let that person in).
Why is the verb lasse before the subject ich?
In German main clauses, the conjugated verb must be in the second position. The demonstrative pronoun den takes up the first position, so the verb lasse comes immediately after it, pushing the subject ich into the third position.
Why is herein at the very end of the sentence?
It is the prefix of the separable verb hereinlassen (to let in). Because the second half of the sentence is a main clause, the conjugated part (lasse) goes to position two, and the separable prefix (herein) gets sent to the very end.