Kowalski watched Private get hatched right before them and called his birth "extraordinary beauty" before they get hit by the goo in the egg.
Kowalski immediately believes Private to be adorable when he was born. Later, he accidentally hurts Private's feelings, by saying they were likely to die (even though Private simply asked if the boys were his family or not).
Kowalski thought his little brother was dead when he was seemingly killed by Dave's Medusa serum ray.
Private is worried when Kowalski and the others are in trouble.
When Private is later revealed to be alive, Kowalski hugs Private and squeezes the life out of him.