Continueing on:
In the extremely rare chances that Xiren does see his sister, they don't really know that they're siblings, and they're just friends for the majority. X and Deem hide this incredibly well, so neither child knows about this, because if they did, things could f**k up terribly, with them asking why they aren't together(It's more or less for finacial things, and so no-one gets concerned or confused when X mentions he's with a robot and not another bird when they do see Xiren. majority of people think Xiren is built by M in this AU, but not the case. So, one runs the main shop while the other runs the bake sale, so they can care for their children comfortably.)
Bun in this AU sometimes gets to visit M, with me bringing her there mainly for healing from battles. (All get along well, and hey. There's a crush floatin' ( ͡° ͜ʖ ͡°) ) Of course, this isn't quite often, since I'm more careful with my battles as time progresses, but I do slowly enter the more dangerous territory with them when I think they're ready. Of course, Xiren watches these battles sometimes with X supervising, since he likes to watch his aunt fight(yes that's still here). Although he's curious about the scar, I mostly make fun of it to make him laugh. Bun enjoys it as well, but not as much as lil' Xiren.
Cherry here is a hella lot more motherly, and lemme tell you this
If you take a woman, who loves their child with their entire heart and soul, and would literally die for them.
And if you take that child away from them.
There is no limit to what that woman can do to get their child back. This includes killing people, forcing information, taking damage, just to get their child back to their arms. Same applies to a guy, as well.
Of course, with Cherry being like this, she's more relectent to letting you go than Toriel is in base game. She really doesn't want to let you go, especially with how dangerous Shadow can be. Of course, not realizing he's living in his own depression and sorrow at this point(even tho he kinda already is, but not the point).
With Flowey, more of a bitch. Stronger than base Flowey/Omega Flowey/Asriel. I mean, he's death, he can use whatever f**king magic he inherited from his parents, and whatever he wants in that state. But in terms of regular base, just death, I guess.