A young couple in poverty give birth to identical twins...
A young couple in poverty give birth to identical twins.
After much consideration they decide that the best thing for the baby boys would be to give them up for adoption so that they can have a better shot in life. One boy goes to a Spanish family who name him Juan, the second goes to an Indian family who name him Amal.
18 years pass when the birth parents receive a package from Juan with a letter saying how grateful he is to them and with a ton of pictures of him and his life. This makes the birth mother inconsolably sad, her husband says “are you not happy? You always wondered what he looked like, whether he had my eyes or your nose and now you know” “I know and I’m really happy that I got to see the pictures but it makes me even sadder that I have no pictures of Amal.” To which the husband replies “they’re identical twins, if you’ve seen Juan you’ve seen Amal!”
This is a bit of a shaggy dog story (although, it could be much longer if the teller cares to tell it that way.) The super lame punchline is mainly funny due to how long it takes to get to it. To explain the pun, there is an idiom "if you've seen one, you've seen them all", which is used to discourage someone from going out of their way to see something that is from a class of things that they have already seen a lot of because there is little marginal benefit from it. The phrase "if you’ve seen Juan you’ve seen Amal!" sounds a lot like the aforementioned phrase, and that is where the pun comes from.