Can 何か be a question word?

Question

The following sentences are from the JP children's book よだかの星:

「ね、まあ、あのくちのおおきいことさ。きっと、かえるの親類か何かなんだよ。」

The 2nd sentence feels like an implied question e.g. "Surely, [he] is kin of a frog or something." (implying that the speaker suspects the nighthawk isn't the kin of a frog, but something else entirely")

But (as far as I know) a sentence that ends in だよ is always declarative unless a "question word" is included. e.g. "Surely, [he] is kin of a frog or something." (The speaker has no suspicions. It's simply a matter of fact that the nighthawk is the kin of either "a frog" or "something").

Now since the expression 何か uses the 何 kanji (which is also used in other interrogative words, like "what") I wondered if 何か in this context could function as a "question word" and carry a questioning tone. e.g. "I am going to do something?"

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Another example of the 1st tone: "My dog is a hound... or something...."
(this sentence isn't technically a question, but it's still implying a question of authenticity and a suspicion that the dog isn't really a hound)

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Another example of the 2nd tone: "My dog is a hound, or something."
(there are no implications in this sentence. It's just a simple matter of fact the dog is either a hound or something else.)

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So, I guess my question has three parts:

1. Can 何か be an interrogative word or indicate a question tone?
2. Does Japanese even have implied questions like this?
3. What's the best translation of that 2nd sentence?

Answer 1

1. Can 何か be a question word?

何か here is not a question word. (「何 + か」 can be a question word in different structures.)
[何]{なに}か here means "something".
「～か何か」 = "~~ or something similar" "~~ or something like that"
(The か in 親類か is a parallel marker / 並立助詞.)

implying that the speaker suspects the nighthawk isn't the kin of a frog, but something else entirely

The sentence means that the speaker suspects the nighthawk is the kin of a frog or something (like a frog / similar to a frog).

2. Does Japanese even have implied questions (and doubt) like English does?

After reading your comment below ("I'm sure he's a frog's cousin or something." could indicate doubt or a question of authenticity. i.e. You don't really think he's a frog's cousin, you think he's something else.), I can't think of a way to directly translate/convey the sentence/meaning into Japanese (without sounding really translated, at least.)

3. What's the best translation of that 2nd sentence?

きっと、かえるの親類か何かなんだよ。
"I'm sure it/he's a frog/toad's cousin or something (similar / like that / of that kind)."
"It/He must be a frog/toad's relative or something (similar / like that / of that kind)."

_{(I don't know if this is the best translation, but it's what it means. Please modify it to what sounds natural in your language.)}