Baby's mind blown by dad's identical twin

A video of a baby's utter confusion when he sees his father's identical twin has been watched more than 12 million times in less than a week.

New York dad Stephen Ratpojanakul posted footage of the amusing encounter on Facebook last Thursday.

The video starts with the father holding his 16-month-old Reed before the baby's uncle Michael takes the child from his twin.

When Michael points at his brother and asks Reed "who's that?" the infant promptly smiles and replies "dada".

Stephen then takes his son back, points at his twin and asks Reed the same question.

After a brief pause and some apparent confusion Reed answers "dada" once again.

Stephen then takes his son back in his arms and without being prompted Reed looks at his uncle and calls him "dada" a second time causing both brothers to erupt in laughter.

The video has proved as popular with internet viewers as with the Ratpojanakul family and has already watched more than 12 million times since going online.