"He likes his dogs."
Translation:Han tycker om sina hundar.
So if I'm talking about the man liking his own dogs, I would NEVER say, "Han tycker om hans hundar" because that would imply there is another man's dogs that he likes?
Ditt, din, dina: belonging to you, the person I am talking to.
Ert, er, era: belonging to you, the people I am talking to.
Hennes: belonging to her (but not the “her” who’s the subject of the sentence)
Hans: belonging to him (but not the “him” who’s the subject of the sentence)
Sitt/sin/sina: belonging to that person who’s the subject of the sentence.