Let him sit in peace

A soldier came back home from the army and found three kids in the house.
Who are they? he asked.
Well, when you were leaving for the army, remember? I was pregnant. So, here
is Kolya. Then remember, when I came to visit you in the garrison? So, here is
Katya.
Yes. But who is the third? The third!
What do you want from him? The kid is sitting quietly, so let him sit in
peace!