What The Son Meme Means
The adoption that does not ask permission.
The line: "he is my son" is the Son claim - the one you make over whoever is standing in front of you, with zero setup and no plan to take it back. It is not literal. It is the move of naming the thing you just saw as yours, in a flat voice, and letting the room figure out how you got there.
Where it landed: the phrase went viral around the Anthony Mackie clips, where the deadpan delivery made the line land like a whole scene - not a joke setup, just a statement that was too strong for the moment. The version that works is the one where the speaker is not performing it. The confidence is doing all the work.
Why it is funny: the humor is the gap between the small situation and the size of the claim. A person in the room, a thing just seen, a very small commitment - and the answer is "he is my son." The line is bigger than the moment, and it is not the person who is bigger. It is the flatness. That is what you are reading for.