Capitalising Unusual Family Titles

I'm aware of the rules around capitalising family titles, so I'd write:

"Last week, my grandma showed me how to fish."
and
"Last week, Grandma showed me how to fish."

But what if the title is an unusual one? I'm thinking of family titles like Oma, Marmee, Nona, and the like. Do they follow the same rules, so that you'd have:

"Last week, my oma/marmee/nona showed me how to fish."
and
"Last week, Oma/Marmee/Nona showed me how to fish."

Thanks in advance.