Tamagotchi ghosts

[dukealien]

They soon stopped feeding them,
forgot to give them exercise,
no water for days, always an excuse,
always me who stepped in
to try and revive them.  This sets up the characters and dynamic effectively.  Use of "me" instead of "I" sets the informal/colloquial tine.

The boys left home,
all their unwanted childhood  "unwanted childhood" is excellent, and singular indicates it's shared between them, and with the parent (speaking)
stashed in boxes,
I found the dead Tamagotchi’s  I cavil slightly at the apostrophe.  It's a foreign word, but no reason the plural should not just add an "s"
at the bottom of an assorted Lego box.  For clarity, perhaps hypen, as "assorted-Legos"  if only because you can make a box out of Legos.

They where buried with memories  hanging here in an ambiguity...
I'd thought forgotten,  and then the reveal - not the boys' own memories but the parent's
I tried for hours to revive her,  going slightly off the rails here:  now there's only one, and it has a gender
but some things  begins to step back from the edge
are just programmed to die.  and back to adult understanding.

If I listen too hard, I can still hear the breathing  and then slips back, but (probably)
on nights when I can’t hold my breath any longer.  thinking of the kids, not their forgotten toys

(Before attempting the requested critique, I must admit this one hit me, personally, very hard.  I tend to assign inanimate objects personalities, and could probably not bear to own a Tamagotchi.  As it happens, I unpacked some old model trains this afternoon and it was... stressful.  But to work.)

This is well done, with some turns, advances and retreats that evoke the viewpoint character's emotional journey.  There's a suggestion the VPC is the mother, and a light suggestion that there was also a girl-child, perhaps stillborn or died young.

The language is suitably plain.  I looked up "Tamagotchi" to be sure, but was almost certain what it was before I came to the word in S.2.  And the evocation of listening for a loved one's breathing, holding one's own, is poignant.

You use "box" twice in S.2.  I'd suggest changing the second instance to "bin" or "carton" for variety.  Maybe "bag."

A few grammatic niggles above, but basically the concept and execution are very solid.