I'm not a native English speaker so I was wondering the differences between small and little. When I was googling, I got the There is an important difference between the words “little” and “small.” The difference is, when describing an amount, we use “little.” But when describing the size of someone or something, we use “small.” Here is an example: The airplane seats are only a good fit for small adults.

But what about "little brother/sister" or "twinkle twinkle little star" or if it's someone's name such as "little Anna" or other nouns such as "little pig". If I'm understanding correct, the adjective I'm using for the example nouns are for the size. But I don't think you use "small" for it?

According to me they both mean the same, It just depends on the situation of usage. Little means small and small means little. Therefore, Little is synonym of small.

The words small and little are synonym in literal sense, but it depends on how you use them in a sentence.

Well, yes you can use both small and little to mean the same thing in a sentence, but when it comes to amount, it's specifically little

You can say " I have little water to drink"

but you can never say " I have small water to drink"

Small is mostly used to describe size, e.g I have a small water bottle.

in the door-way, with his head in the room and with a lantern in hand with the most slight ray of light shining from it; so small and opening it so slowly to not disturb the old mans sleep.

i have watched the play of this story last friday.