他（ほか）に is regularly considered to be one of the more difficult structures to master in Japanese, so let’s take a thorough look at it. Basically,
他（ほか） by itself just means ‘another’, or ‘other’.
に highlights
他（ほか） ‘another thing’ as being the target of what comes next in any particular sentence. The possibilities are as follows:
他（ほか）に - Another thing.
他（ほか）に（
も） - Even another thing (sounds less certain).
他（ほか）に（
は） - Was there another thing (focuses on something pre-existing, which someone may have forgotten).
-
他（ほか）に、欲（ほ）しいものはある？
Is there anything else you want?
-
動物園（どうぶつえん）の他（ほか）にもどこかへ行（い）きますか。
Is there anywhere else you want to go, other than the zoo?
-
他（ほか）にはない物（もの）が食（た）べたい。
I want to eat something that isn't anywhere else. (Something unique to this place)
他（ほか）の + Noun - Another ‘specific thing’.
他（ほか）に（
は） may be used in either positive or negative sentences, but it tends to appear in negative sentences more often.
-
お金（かね）の他（ほか）には何（なに）が欲（ほ）しいですか。
Other than money, what do you want?
-
彼（かれ）の他（ほか）にはフランス語（ご）を話（はな）せる人（ひと）はいません。
Other than him, there isn't anyone else that can speak French.
Because
他（ほか）に（
も） focuses on the ‘addition’ of another thing, it cannot be used in negative sentences (with the exception of questions).
-
欲（ほ）しいものは、その他（ほか）にもない。
There is also nothing else besides what I want. (Unnatural Japanese)
-
その他（ほか）にも何（なに）か質問（しつもん）がありませんか？
Besides that, are there no other questions? (Natural Japanese)
The reason this is acceptable in questions, but not statements, is due to the ‘isn’t it?’ meaning that negative questions can have in Japanese (just like English). It is the equivalent of the following:
この他（ほか）にもない - In addition to this, there is also nothing (sounds strange in English!)
その他（ほか）にもないか - In addition to that, is there nothing else? (sounds normal in English!)