It's not Vin, and we only hear at one point about the siblings.
Last little hint, if no one gets it I'll solve.
Not Adolin
Not Syl
Not Sarene
Not Adrotagia
Not Kaladin
Not the Stormfather
Not the Sibling
Not Rock
Not Vin
1. This character lost someone they loved.
2. This character moved to improve themselves.
3. This character has two siblings.
4. This character is not forgiving.
5. This character has quite a profound influence on a main character.
Bonus: This character has a special visitor every first of the month.
Bonus 2: The visitor each month is the main characters of clue #5.