I'm not sure how much you care about the meta aspects of Deltarune, but what are your thoughts on Gaster and him also embodying a parental/brotherly dynamic (most likely with Sans and Papyrus)?
I'll be honest with you chief. I am like Gaster's weakest soldier so my answer probably won't be satisfactory to true Gaster fans.
But since you gave me the opportunity to yap about my thoughts regarding him I'll yap regardless even if I can't give similar insights like some of the other true Gaster fans.
To me something to keep in mind about his character is his parallels specifically Flowey and Gerson.
Two individuals that were brought back in unconventional ways just like how Gaster got shattered into time and space yet still is kicking around today in deltarune.
We know that he has some connection with the skeleton bros possibly being an older family member either as the third older brother or straight up their dad.
This gives us some insight on their family dynamic. If he was the oldest then his absence seems to echo a similar hole in his family just like Gerson's and Asriel's absence echoed a hole in their family.
In Gaster's case since he is implied to be the oldest it is pretty reasonable to assume that he had the task of providing for his family something that was probably shifted over to Sans since in the japanese text he's implied to be the older one out of the two.
Something to keep in mind that like Flowey and Gerson Gaster can't reach his family due to him reaching into a seemingly higher plane of existence which means he probably can only watch his family from a distance and never can interact with them.
Another thing to keep in mind is that we don't yet understand what Sans and Papyrus feel about this. We know they are both aware of something but their general feelings regarding the matter isn't exactly shared. There is a slight chance they might have forgotten him but even that isn't unclear.
It's implied that Papyrus remembers some of his time in Hometown from the interview but even then it's unclear if he's suffering from amensia or he was genuinely young when deltarune was taking place.
There is a genuine mystery regarding Gaster and what his family feels about which to me possibly indicates that they have either forgotten about him or much more likely that whatever is happening with Gaster is a very very personal matter that they don't share with locals willy nilly. Which. Considering his implied circumstance yeah i could understand that.
As for Gaster he seemingly doesn't talk about his family that much possibly because he is suffering from similar circumstances to Flowey where his family can no longer make him feel whole anymore due to his odd circumstances.
Which leads him to focus on his experiments since that's all he could do honestly.
However like Gerson while he himself can't reach his family himself he can make someone else reach from them instead (just like Susie reached Alvin). That someone being of course...
Kris.
Something to keep in mind is that Gaster presence only started showing up majorly after the skeleton family more specifically Sans started to get close to Toriel.
And this is important because Sans seems to be building more into the family drama as he seemingly is getting closer and is establishing himself in their household.
Whether romantic or not the skeleton family are now seemingly involved with the Hometown drama which is at the center of practically everything in deltarune and this explains the role of Gaster involvement in that plotline specifically.
Because Gaster is not just this incompressible god that is untouched and is just interacting with the world on a meta level but rather he's also family.
His involvement with Kris is not just because he wants to mess them up specifically but because they could genuinely be considered his goddamn grandchild.
Like Gerson he is more concerned with them than any other member of his family because to some extent Kris is the last remaining connection with his family. He's clearly involved with their soul and seemingly more interested in what the Soul (the culmination of Kris's being) wants than literally with anything else.
This is why Gaster seemingly does not care about any of the Soul's decisions. If the Soul wants to quit cool, it wants to do a weird route also cool. Gaster literally does not care about Soul's decisions he only cares that the Soul is making the decision which could absolutely read as a scientist taking notes it could also be read as an older family member seemingly not interfering on how their grandchild may want to play the game.
Especially when you remember how he cheered for them in the knight fight. He genuinely wants them to win.
He involvement with Kris is to some extent personal and that makes sense when you understand his circumstance he has reached into a plane of existence where he could only look down upon the world where his family can't fill the void in his heart.
But he still knows what deltarune is. Just like Gerson he understands this perfectly and while Gerson's eyes on Susie who will bring hope to this story Gaster is seemingly most interested in Kris who is the literal heart of deltarune the character who strings connect to every person, every seceneray, every music, every place of deltarune something Gaster is in love with also it makes sense for him to be attached to them.
Furthermore:-
Kris is someone who is driven like him.
Someone who can't be understood by their loved ones like him.
Where their loved ones can't fill the void in their heart.
Someone associated with hell and heaven and hands.
Someone who seems to be splitting just like how he shattered into pieces.
Gaster is genuinely enamoured by their light and considering that he seems to be aware of the prophecy he to some extent always knew that they were destined to become family and seeing how similar they are he seems to latch more on them than any other member of his family.
And it's possible that just like how Susie was used to reach through Alvin even if Alvin wasn't fully aware of it regardless it seems like something similar will happen with Kris too. Just not sure what considering that currently they are in conflict with him due to you know getting close to Toriel. Oh well I guess we'll see.
In short i think Gaster's relationship with his family isn't fully explained however through his parallels we can possibly detect that he is seemingly detached from them due to his circumstance meanwhile for Sans or Papyrus he seems to be either a touchy subject or a person they don't exactly remember futhmore they way Gaster seems to be integrated through the Hometown plotline is through his family getting closer to the Dreemurrs which by proxy made him some varsion of an older parental figure in Kris's life (i said grandpa mostly because it was easier to say and also because of the existence of grandpa Semi but honestly he could also just as easily be read as their uncle) and considering what we see from Susie it's clear to me that whatever presence Kris seems to have in Sans and Papyrus life is meant to be extentstion of Gaster will.
Think of it like being his way of connection with his family.
Where it's through Kris that Gaster could have a semblance of connection with his family after getting shattered and seemingly becoming more detached.
And yeah that's my thoughts on Gaster and his parental role in Sans and Papyrus life. Obviously i am not a true Gaster fan so i probably miss something but hey it gave me the opportunity to yap about my thoughts regarding him.
Thank you for the ask.
