This is the 514th most frequent Icelandic word.
mínum
"Mine" (possessive, dative plural of "mínn").
In this sentence, 'mínum' is used in its possessive dative plural form to denote 'to my' in relation to 'foreldrum', which means 'parents', indicating a dative relationship.
Björn og Hrafn eru vinir mínum foreldrum.
Björn and Hrafn are friends to my parents.
Here, 'mínum' refers to possessions ('my' abilities) in the dative plural form as required by the verb 'trúa' (to believe/trust), which governs the dative case for its object.
Ég trúi á hæfileika mínum.
I believe in my abilities.
The word 'mínum' is the possessive form used to indicate ownership by 'my' (first person singular) in relation to the noun 'vinum' (friends), indicating 'my friends' in the dative plural form.