Adoptive dilemma

I’ve wanted to fix lack of tags such as sisters, aunt and niece, mother and daughter and so on.
However I did stumble upon a roadblock. There are several instances of adopted family which I’m unsure if I’m clear to add (like Spike being adopted Twilight’s brother or royal sisters being adoptive aunts to Cadence), should I add these too or would they be too confusing?

Please do not tag things like that.

Could one append the word “adoptive” to the beginning of such tags and that would be acceptable? At least in cases where it is both clear(a) and not spammy(b)? Maybe only images where the relationship is shawcased and clear (or the tag vague such as “adoptive family”).
(a) While Spike is pretty clearly family to Twilight, “brother”, “son”, and “indefinable” are all options for what sort of adoptive relationship it is.
(b) Tagging every appearance of Cadance with either of the diarchs with “adoptive aunt and niece” seems like it COULD be a bit repetitive/redundant and still more for images of Cadance without either of the diarchs?