Tattooing A Baby?

I just read this article, and I guess it's also starting to go viral, but basically the father of two twin boys wants to be able to tattoo one of them, because they were born prematurely and one of them is perfectly healthy, Adam, and the other has a disease that makes it so he has to take a medication every 4 hours, his name is Aaron. Since they are identical it's hard for even the parents to tell them apart, and recently while visiting their grandmother, she gave them a bath and the marker dot they have on Aaron washed off and she accidentally gave the medication to Adam. Both toddlers where in the hospital, because one didn't get the medication they need to live and the other got a medication he isn't supposed to take and it made him extremely sick. It scared the father so much of it happening again that he wants to permanently mark Aaron so it'll be impossible to mix them up again, and he wants to do it with a tattoo. What are your guys' opinions on this matter?

I personally think he should just give them both completely different haircuts or even pierce Aaron's ears, a tattoo is probably the most insane and extreme way to go.