word usage - Distinguish twins vs distinguish between twins

I'm confused about the use of the word "Distinguish". The link shows an example sentence where the verb is used as an intransitive verb:

Can the child distinguish between right and wrong?

But I find it difficult to see the difference between these two sentences:

1. I find it hard to distinguish these two twins.


2. I find it hard to distinguish between these two twins.

Is there any difference between the two sentences or do they have the same meaning? If they don't have the same meaning, in which context do you use one over the other?