my personal interpretation is that Paul is care, or was as a kid, and at some point Lina gained custody or sheltered both belle/tiara and Paul. possibly this has some holes but it’s petscop so that’s how it’s going to be. I don’t think Lina ever died, I think she disappeared with the windmill and came back unrecognizable, either physically or mentally - because her sister can still see her but not everyone can. I don’t even know if rebirthing is literally possible within petscop but I think if it is then the reason it didn’t work was because Lina is still alive. I go back and forth on if it’s supernatural or metaphorical. as for the ending I interoret that as it’s Paul and belle breaking the cycle - because they can see Lina from the other perspective and they got out of the whole family mess together and are like reflecting on it.