Yes, they're all family. Belator can be the dad.
Kurt's painting has finally been delivered; thank goodness! Miramira really just acquired Cathié like that.
I suspect Cathié has connections to someone in Quovelta; maybe Tania, who was mentioned in the previous chapter? After all, she is staying outside for extended periods of time, and Quovelta is known to be around the area. Though, everything she said about her mom being bossy might be the simpler explanation for her behavior. I guess we will have to see.
Cathié really reminds me of young Nona for some reason. Nona is definitely projecting onto her too. Interestingly, Cathié mentioned that "stuff happened" that put her mom's job on break and made Mrs. Roz start to stay at home... Could the family be hiding a mage or something?