So I don't know exactly how went the story of Shortcut and Sage. The live with Recall!Error and his Reaper, right? And...where did their Sans father end up?
Oh no, Shorty and Sage doesnt live with them lol, they just pop in for the asks.(images below to illustrate who belong to which family)
Their Sans "father" is still around actually, tho he end up into two(Classic and Sansti) due to a split in the timeline. Same goes for their Geno and Error(whom is now Queeno(dead) and King Error, and Geno(dead) and BadSans!Error).
Oh, the two timelines hadnt clashed with each other so no meet ups yet('cept for brief ones like these)
and Shortcut and Sage lives with the unglitched Sans with their Uncle Pap in the omega timeline(they're the only survivors after Geno agreed with Error to destroy their au) Read some more about it here