please someone tell me the differences between sin and hans its very confusing to me thanks
"Hans" is referring to a man. But if you have already mentioned this man in the phrase, and you want to point out that something is his, you should "sin". If you use "hans" again, you'll be referring to a second man. The "sin" particle doesn't have any genders, so it'll work for "hun" as well.
Here's a reason why "sin" is needed. Imagine that Astrid is walking with her husband Bjorn, and they meet Ingrid and her husband Sven. Astrid says hi to Ingrid. Astrid kisses her husband.
Excuse me, WHOSE husband is she kissing? It's not clear ... so in the interest of preserving both her and her friends' marriages, you must use "sin" here. :) It shows that the pronoun is indeed reflexive.
It's one of the constructs that make the Nordic languages so cool.
Sin/sitt/sine refer to something already mentioned in the phrase.
Mannen og hunden sin
The man and his dog (the dog of "mann")
However, if you use "hans", it will cause ambiguity and confusion.
Mannen og hunden hans
The person reading this will think "His dog? Whose dog?". "Hans" implies there's a third person.
Unfortunately, that doesn't work in this case. In the sentence "mannen går tur med hunden sin" ("the man walks his dog"), "sin" would have to be used if the man was the same, and the use of "hans" would imply another man, as you say. But in "mannen og hunden sin", "sin" can't refer to the man, it has to refer to something earlier in the sentence ("hun går tur med mannen og hunden sin", where "sin" refers to "hun"). The reflexive pronoun has to refer to a different constituent in the sentence (normally the subject, but it can also be the object).
Ok, I think the main problem with grasping this is that the reflexive pronoun is possessive. Let's start with the personal reflexive pronoun, which has an English parallell:
"Han vasker seg" = "He washes himself"
In this sentence, we have the typical situation for use of reflexive pronuns: the reflexive is the object of the sentence, and it refers back to the subject (in a situation where the two are the same person). This can work as a simple rule that will hold in almost all cases - the reflexive is an object (in a loose sense, i.e. pretty much anything that isn't the subject), and refers back to the subject.
Possessive reflexives are harder to grasp, because they don't exist in English (and many other languages). But the basic rule is the same: you will find the reflexive in the object (but it will not BE the object since it works like an adjective and has to be used together with a noun), and it refers back to the subject.
This also means that you cannot judge the correctness of a usage unless you have a complete sentence. Your example "Mannen og hunden sin" is not grammatically incorrect, and can be used in a sentence, BUT it cannot mean that the dog is the man's, and the reason for that is that this meaning would require the man to be the subject of the sentence and the dog (having the reflexive pronoun attached to it) to be the object. But bound together with "og" it can't be both, just EITHER the subject OR the object as a unit.
So you can say:
- Mannen slår hunden sin - The man beats his (own) dog
- Kvinnen slår mannen og hunden sin - The woman beats the man and HER (own) dog (in fact, I'd understand that as "her husband" as well)
You can NOT say: - *Mannen og hunden sin går tur - The man and his dog go for a walk (because that's simply not a grammatically acceptable sentence: the reflexive cannot be part of the subject, it has to refer to the subject but be outside it).
Keep in mind that this is not logical, it's just grammar.
Also, if you know German, it's important to NOT get confused by "der Mann und sein Hund" and the like. The German "sein" is not reflexive, it's just a regular personal pronoun meaning "his".