"I am her husband."
Translation:Jeg er hendes mand.
"Sin/sit/sine" are used when the object is owned by the subject (in third person and singular). For example:
Jeg/Du har min/din bog (I/You have my/your book);
De/I har deres/jeres bog (They/You (all) have their/your book);
but Han/Hun/Det/Karoline har sin bog (He/She/It/Karoline has his/her/its book [if the book belongs to them]);
or Han/Hun/Det/Karoline har hans/hendes/dets/Karolines bog (He/She/It/Karoline has his/her/its/Karoline's book [if the book does not belong to them])