The English provided here is sound. Are you saying the English translation of the Russian sentence is incorrect, or are you saying that your translation is the preferred one? Because I'd have to respond with 'wrong' on both counts.
Whereas it is uncommon in most countries today not to have more than one wife, it is definitely not unheard of. 'He has no wives' is an equally valid statement.
Similarly, if someone asks 'Wasn't Jimmy Tom's brother?' one might respond with either 'He has no brothers' as well as 'He has no brother'. Both are correct and would not make anyone confused about the intended meaning.
You cannot say that is not the case here, because the only thing provided by Duo is the one sentence, which is the response to a statement that we do not have. It might very well be that they are referring to Jimmy, and therefor the singular form. We do not know. All we have is the one sentence and the only thing you have to do is translate this particular sentence as best and as accurate as you can.
Translating it to 'he does not have brothers' is not correct, as they have provided the singular form of the noun here. Duo does not care about the preferred canonical form. What it cares about is teaching you the appropriate use of the genitive case for the singular form of the noun and the correct use of the proposition that comes with it in this sentence.
Duo is trying to teach you Russian. It is not trying to help you improve your English. Keep it simple.
Obviously, it would be impossible to provide the context in a single sentence (which is the teaching method of Duolingo), and that is why the canonical form is specially relevant here. That is keeping things simple! On the other hand, any language teaching method prioritizes canonical forms, when you know the rule, you, as a learner, can explore the exceptions. This is not only true for English, this is a general rule for learning any language.
You may think that it is impossible to learn a language without context, and it is true that modern language teaching methods work with language in context, but, anyway, Duolingo's methodology can be improved providing examples of language use that are not exceptional. According to szeraja_zhaba's opinion as a native Russian speaker, the use of "have no" is similar in English. I wouldn't provide a exception as an example to a beginner without explaining why I choose to use it.
I am in agreement with you when you say it could be helpful for Duolingo to provide canonical structures. At this moment, however, they do not. Which means that any sentence provided should be treated as a singular and separate entity, which is to be translated as-is. Simple enough, I'd say.
I do admit that my opinion in the matter is possibly a result of my own native language considering both of these sentences as correct and therefore acceptable.
My translation is preferred in English
It might be a preferred sentence, but it's definitely not a preferable translation. In fact, it's a translation of a different sentence:
- У него нет брата = He does not have a brother
- У него нет братьев = He does not have brothers
To have no + plural countable noun is the canonical form, but Duolingo marks it as a mistake. The canonical English structure should be perfectly used as a translation, because in English it indicates both possibilities, due to it is the unmarked form. You can consult any English grammar book to find information about this.
I am editing this message because I cannot reply your new comment, szeraja_zhaba. I cannot consult a Russian grammar because I do not speak Russian. I would not be here if I spoke Russian!!! If what you say is right, I do not understand why Duolingo does not use canonical forms in early stages of Russian language teaching. They should start with the common usage structures and only then approach special cases like this.
I think Russian is pretty much the same in this respect. «У него нет братьев» would be used by default, unless you have a reason to speak specifically about one brother.
I don't know good grammar books to refer you to, but I believe the structure is the same in English and in Russian, so your translation shouldn't be accepted since you're translating a different sentence.
I don't really understand how Genitive case is connected to "-ing". :o I think they're completely different things.
Well, as for cases, basically Russian nouns have several form. For example, nominative case is used for subject of the sentence and for both nouns in "X is Y"-type sentences. Most other cases have several possible uses.
The most obvious use of genitive is indicating possession: if you put it after any noun, it will mean a possessor. E.g. in «дом Мари́ны» 'Marina's house', Мари́ны is Genitive.
Other use of genitive case is indicating absence. You use it after «нет», and sometimes, when the verb is negated, its object is in genitive (не зна́ть сло́в 'not to know the words'; сло́в is Genitive).
«Нет» always requires genitive: «нет воды» 'there is no water', «нет бра́тьев» 'there are no brothers', «нет ве́тра» 'there is no wind'.
Another prominent use of genitive is indicating possession: «температу́ра воды́» 'temperature of the water', «исто́рия бра́тьев» 'the brothers' story', «направле́ние ве́тра» 'direction of the wind, wind direction'.
Genitive is often used in negative sentences, when denoting an object: «Я не пила́ воды́» 'I didn't drink water', However, it's never used when talking about living people. Accusative is also used in this function, and accusative is more common. Genitive works best for abstract things and uncountable nouns.
Sometimes genitive is used for a direct object in positive statements and questions. Then, it has the meaning 'some, part of': Я вы́пила воды́ 'I drank some water'. Accusative is more common for direct objects: Я вы́пила во́ду. I've drank the water.
Some prepositions require genitive: у воды́ 'near the water', у бра́тьев 'at the brothers' possession, at the brothers' place', из воды́ 'out of the water', от бра́тьев 'from the brothers'.
There's no way "a different exercise" actually said that, so you probably remembered it incorrectly. The correct sentence would be "у него нет сестры". Or it could be "у него не сестра" but that one doesn't work well as a standalone sentence and requires a continuation like "у него не сестра, а брат" ("It's not a sister that he has, but a brother").
So, if I understood correctly, его is for positive and него is for negative?
No, not really. Н- appears when the preposition is used before the pronoun starting in е- (у + его = у него), except when the pronoun modifies another word (у + его брата = у его брата).
Negation is expressed by «нет» here. «Нет» + genitive case expresses absence of something (нет брата = there is no brother), and «у» + genitive expresses the possessor (у него́ нет бра́та = he doesn't have a brother).
No, here the preposition is related only to «него», and then the construction «у него» refers to the whole sentence (or to «нет» as the main word in the sentence): ([у него] [нет брата]).
«Брата» is connected to «нет», not to «у него».
Nope, it not just you. The [g] is not there. Его and the adjectival Genitive endings -ого/-его are all pronounced with a [v]. You can hear it in этого, синего, хорошего, большого, какого, моего etc. Also in сегодня "today".
The г you see in these forms is a historical spelling.