terminology

the Littles generally call my partners "Aunty" (yes, even the very blokey one) and obviously the partners call them back by their name (occasionally they aren't clear which Little it is and have to ask but it's usually reasonably obvious*)
But i hadn't thought, until just now when i needed to write something, of what's the right descriptive word for their relationship. In-System-neicelings was my not-very-satisfactory temporary solution but it doesn't really sound right.
Any suggestions?

We use Meta-baby/meta-Small for the poly-molecule (chronological) children so that isn't usable for this


*this is why we are slightly obsessive about signing texts because you can't always be obvious i that few charterers - though dwoucke and judiff both have fairly idiosyncratic spelling and phraseology