Kinship names are the words we use to indicate family members, like mum, mom, dad, aunt etc.
Capitalise when the name immediately precedes a personal name, or when the name is used alone in place of an actual name. So:
Did you remember to get Mum a birthday card?
We went to see Dad when he was in hospital.
Lily and Joe loved visiting Aunt Susie’s house.
I was seven when I last saw Grandma.
Don’t capitalise when these words follow the personal name, when they don’t refer to a specific person or when they are used with possessive nouns or pronouns.
The Sinfield sisters always stuck together.
There aren’t many dads who would do that.
My aunt wasn’t feeling well.
I bought a card for my mum.
Sally’s grandma lived next door.