Following Aizay's visit this morning, during which he got to see his mother interacting with the new baby, I took him to daycare for a few hours. As we neared the end of the ride, Aizay started to cry, saying that he wanted hugs from Mommy. By the time we'd arrived. he'd lost control, sobbing "Mommy, mommy, mommy" ad infinitum. Eventually, after much consoling, I left him there, still sobbing for his mother.
I think he suddenly grasped the finer implications of having a new sibling...and wasn't happy about it.