Japanese words for family in a story
I know that in Japanese there are different words for relatives when you talk about your own family or someone else's family.
But what if I'm writing a story from the third-person perspective and describing my protagonist's family?
For example, "Her name is ... . She lives with her mother, father and younger brother." Should I use 母, 父, 弟, or お母さん, お父さん, 弟さん?