FAMILY RELATIONSHIPS
Capitalize familial names when the relationship is considered part of the personal name or when the relationship alone is used as a proper name:
Uncle Bob
Cousin Snowie
Mother, Mom, Father, Dad
Godmother
Do not capitalize the family relationship when it is preceded by a possessive pronoun:
her cousin Snowie
my mother
Set off the name with commas when only one person bears the relationship:
his son, Robert, came too (only son)
his son Robert came too (more than one son)
my wife, Michaeline, came too