Fun fact for Eclipse for Remnants:
Rosalba and Heloise's parents were in a polycule and the dissolving of the polycule ranged from sudden to messy.
Yes, a brother and sister were in the polycule. No, the siblings were not dating. They barely got along and it was only their shared boyfriend/husband and girlfriend/wife that ever kept the sister from killing her brother.
The relationship(s) was as follows:
Fafner X Nila: Married, technically divorced when Nila abandoned the polycule. Parents of Heloise. An immovable object (Nila) met an unrelenting force that was also an immovable object (Fafner).
Fafner X Corvan: Hard to pin down exactly, but the breakup was messy after Rosetta disappeared. Corvan still shows up from time to time to take care of the girls, but these two have not been in the same room for nine years now. Corvan still clearly cares about Fafner, but Fafner refuses to even hear about Corvan.
Corvan and Nila: The siblings/twins, they rarely if ever got along, though Corvan got along with Nila better than the rest of their family.
Corvan X Rosetta: Very cute and wholesome. Rosetta was one of the few people who could make Corvan flustered and she used this for evil (embarrassing him in front of the polycule). Got married so that Corvan could take Rosetta's last name and cut ties with the rest of his family.
Fafner X Rosetta: Idiots in love, had an awkward phase where they didn't know how to interact with one another when they started falling in love. Parents of Rosalba. Rosetta disappeared nine years ago and is presumed dead, her loss pushed Fafner over the edge and he buried himself in work and into himself.
Nila X Rosetta: Tsundere (Nila) x sunshine (Rosetta). Rosetta used tough love on Nila and it was super effective~! Not effective enough to keep Nila from panicking and running away not long after Heloise was born. Rosetta stepped up to raise Heloise as her own daughter, even after having Rosalba.