Question about English: My sister and I vs. My sister and me
In duolingo for Germans learning English there is an exersise Meine Schwester und ich schwimmen im Schwimmbad. - My sister and I swim in the pool. (https://www.duolingo.com/comment/7329194) After two years no one answered the question, why it is not "My sister and me...".
I suppose, that it could be "My sister and I swim in the pool." but "The persons who swim in the pool, are my sister and me."
Could you as English native speakers help please? If I am right, and in general what is the difference between them in Nominative use. (Why it is "He hit my sister and me.", is clear.)
"My sister and me swim in the pool" is wrong in English for the same reason that Meine Schwester und mich schwimmen im Schwimmbad is wrong in German. Use nominative for the subject of the sentence. That's true even when you have a compound subject like "My sister and I" or "He and she are swimming in the pool."
One of your other example sentences deserves some more explanation: "The persons who swim in the pool, are my sister and me."
The nominative is grammatically correct here, too. (I would say "people" here instead of persons, btw):
"The people who swim in the pool are my sister and I." --correct
That is grammatically correct, but it sounds Very Formal and it can sound inappropriately formal in colloquial / friendly speech. It depends on your audience. In colloquial speech we tend to avoid nominative pronouns at the end of the sentence like that and just replace them with objective pronouns. So although it is less grammatically correct, you will more commonly hear what you wrote:
"The people who swim in the pool are my sister and me." --not correct according to textbooks, but commonly used and doesn't sound bad or uneducated.
As another example, if you call somebody you know well on the phone and introduce yourself by saying "It is I," you will be grammatically correct but sound weird. The normal thing to say is "It's me."
To clarify, the reason that both "The people who swim in the pool are my sister and I" and "He hit my sister and me" are correct is because "are" is a linking verb and "hit" is a transitive verb. The relevant difference between the phrases is that the linking verb redefines the subject "people" as "my sister and I" (all nominative case), whereas the transitive verb connects the subject "He" to the object "me and my sister."
The way I learned it is to remove the other part of the subject and see if it makes sense that way. In this case, remove "My sister and", and read the sentence with what's left.
"I swim in the pool" rather than "Me swims in the pool." Thus, "My sister and I swim in the pool" rather than "My sister and me swim in the pool."
In the predicate it works the other way around.
"The dog chased me" rather than "The dog chased I." Thus, "The dog chased my sister and me," is better grammatically than "The dog chased my sister and I."
i agree with everything jsiehler says. However, in many parts of England, you will hear the "wrong" versions so often, that they might as well be correct.
Even if my sister and I throw some boomerangs which return to my sister and me, you will certainly hear many people say;
"my sister and me throw some boomerangs which return to my sister and I"
10000 lemmings can't all be wrong :)
If you're looking for comprehension, English speakers will generally understand My sister and I and My sister and me equally. You can exchange them as much as you want in any context and your meaning will get across.
In terms of how much English speakers use each, that generally depends on formality, dialect, and education. In less prestigious dialects or among speakers with lower education, and me forms are used more often:
My sister and me went swimming.
The dog chased my sister and me.
In more prestigious dialects, among more educated people, or in more formal settings, and I forms are used more often:
My sister and I went swimming.
The dog chased my sister and I.
For formal writing or formal speaking (if you want to be super correct all the time), use the pronouns like you would in German:
und ich > and I
und mich > and me
Some people think that the last method is the most correct way of speaking; others would say it is too elitist. My mother studied language at college and works as an independent editor and publisher of books, and she is a stickler for grammar. She is very particular about English grammar, and even she uses and I where and me would be more technically correct (like Don't forget to pick up your sister and I. where Don't forget to pick up your sister and me. is more technically correct).
English speakers (even native-speaking grammar sticklers) rarely get all of it right, so don't worry about it too much. As a rule of thumb, using and me for und ich makes you sound uneducated or informal, and using and I for und mich is generally passable unless someone is being really picky. Note that this only works after words like and, but, and or; saying Me stood at the door or He gave it to I are very very nonstandard. When in doubt, do as you would in German, and you'll probably be fine.
In more prestigious dialects, among more educated people, or in more formal settings, and I forms are used more often: My sister and I went swimming. The dog chased my sister and I.
I hate to disagree, since you are clearly educated, but whilst you often hear: The dog chased my sister and I, it surely cannot be due to being more educated, rather the opposite...
The dog chased my sister and I is wrong, since sister and I/me is the object of the verb chased. My sister and I swim is more correct, but you're right, you often hear my sister and me swim. Especially if the sentence is in the middle of a conversation. I think I and me may be slowly melting together in terms of usage.
Probably the reason no one responded for so long is that most English speakers don't really know the rules of grammar, so they just have this vague feeling that it "looks wrong". Also, as others have said, lots of English speakers say "My sister and me" inappropriately. Actually, I suspect I've been guilty of that myself on more than a few occasions.