1x1/2 reads as "1 cross 1/2", so 1 and a half are crossing each other.
Now we could even think of this as a prophecy about how the manga is going to end, since crossing means that you'll go from a point far away to a point with equal terms to another point far away, meaning the "relationship" would go from family to lovers to family.
Why does Yuri manga always involve some sort of weird melodrama?
Because without melodrama it's just hentai about two women depraved to satisfy their sexual urges.
It's as easy as it is.
The genetic bonding between same sex-"couples" is weaker as they don't procreate.
They are also religiously unacceptable (at least in modern society), so they don't have any common ground to share.
What we have nowadays in society for "gay acceptance" is part of an ideology that wants to destroy modern societies by separating men and women with Feminism, Abortion, promiscuity and LGBTQ+-indoctrination.
Intelligent people don't buy that doctrine after suffering from 20th century doctrines (socialism, national socialism, communism all called for the suffering and irrational behaviour of the masses for the sake of minorities & social elites) all over the world.
This means that melodrama is enforced as long as the manga wants to tackle the theme realistically and seriously.
To be honest, the manga is pretty strange in the first place since it tones down the "lesbianism"-theme in favor of the "incest"-theme.
Before all, it should be strange that there is this abnormal attraction between two women.
Yet all the characters confronted with it seem to not mind it at all(they only mind the mother-daugther relationship), meaning it's either a completely indoctrinated world (surreal as to speak) or it's a fantasy world where only part of social rules apply.
Now here's the question:
How do you build a plot that is not controversial at all in its universe/setting without involving other genres like action, fantasy, isekai,etc.?
By adding a melodramatic subplot.
Still, this gets stranger by the chapter. I'm actually curious how the author wants to patch up this sinking ship without presenting us with a deus ex machina...