Oma and Opa are the german and dutch words for grandmother and grandfather, my father's parents were always known to me as Oma and Opa, almost never used their names Beatrix and Johannes... their siblings, i don't remember the word for uncle but for great aunty, "Tanta" or something like this

i remember at the age of 4 years old when we would visit them (for a time we lived in an adjacent property) there would always be kisses for both Oma and Opa at greeting, one on each cheek