"Mia patrino kisis mian malgrandan fratinon."

Translation: My mother kissed my little sister.

[Interrobang3]

Then turned her head to me, nodded, and left. She never did love me as much.

[deactivated user]

Does this mean little as in younger or as in size?

[qubist]

I would guess that, as in English, it's both. Little in English doesn't mean young, but in the context of a "little sister" we understand it as meaning "younger sister".