Galadriel and Aredhel are, of course, not Maglor's siblings. Maglor would likely have his hands full if he's given responsibilities for his 5 younger brothers, though, so same idea. There is no clear indication that Galadriel and Aredhel are friends with one another, but I certainly wouldn't mind if we went that direction.
I do like the idea of the cousins and half-cousins running wild in Tirion, going exploring, and having scenes with each other that don't directly involve their parents.
Siblings - Fingon, Turgon*, Aredhel^ (children of Fingolfin and Anairë)
and their full cousins Finrod*, Aegnor^, Angrod*, and Galadriel^ (children of Finarfin and Eärwen)
and their half-cousins Maedhros, Maglor*, Celegorm^, Curufin*, Caranthir^, Amrod and Amras (sons of Fëanor and Nerdanel).
(Not to mention that Finarfin's kids have cousins in Alqualondë - Eärwen's brothers' kids)
There are friendships across these families - Fingon and Maedhros are best buds forever, and Celegorm and Curufin are friends with Aredhel. Finrod seems to get along with Fingon and Maedhros somewhat (he is on a hunting trip with them when he meets Bëor) and also Turgon (they are travelling together when they get the dreams for Nargothrond and Gondolin). All of the sons of Finarfin get along with the sons of Fingolfin, IIRC, which explains them going into Exile when Finarfin backs out of the rebellion.
And lest it sound too much like everyone is buddy-buddy except for Fingolfin and Fëanor, I have to also point out that Caranthir and Angrod really don't like each other at all. And....Galadriel and Aredhel are very....SEPARATE, for being the only two granddaughters.
* indicates wife/gf who may be introduced, but maybe not. The only one we need 100% by the end of the season is Turgon's wife Elenwë of the Vanyar (and their child Idril). Finrod's lady love Amarië of the Vanyar will show up early next season when she refuses to go with him into exile, so likely will appear at the Feast at the end of this season as his girlfriend. Curufin's wife is totally unknown, but Celebrimbor comes from somewhere, and this is his last chance to meet Fëanor. Angrod's wife Eldalotë in a Noldo. Maglor's wife is totally unknown.
^indicates someone who *must* be single at the time of the Darkening of Valinor (ie, they will have romantic stories later). Caranthir is iffy, but people consider his interest in Haleth a rough attempt at courting and thus keeping him single until then is probably preferred.
You will note that neither Fingon nor Maedhros is listed as having a romantic interest at this time, nor a story for later. IF Fingon were to be Gil-galad's father (rather than Orodreth), that would be different. The fandom has already decided, of course, that they are too into each other to notice anyone else.