彼がいつ来るか

when he will come

→ 彼
phrase Rare #37,004
when he will come Used as an embedded question meaning “when he will come.” The か at the end marks the indirect question.
JA: 彼がいつ来るか知っていますか。
EN: Do you know when he will come?

彼がいつ来るかよくわからない

I'm not sure when he'll come.

彼がいつ来るか分かりません

I don't know when he'll come.

次に彼がいつ来るかわからないんだ

I don’t know when he’ll come next.

彼がいつ来るかわからない来れば最善を尽くすだろう

I don't know when he'll come, but when he does, he'll do his best.