Although from what I can tell, Parents who kill their children tend to be looked down upon, but it seems like the other kos are either landing or watching their sibling die.
They're all definitely dying babies in the last panel judging by the sfx they're making and all the little "yu"s. And it's not like they can open their eyes or talk properly enough to tattle on Marisa. She's totally in the clear. But yes, parents that kill their children are generally shunned and hated.