nov 8, 2012 - Harry gets the Swallows tattoos

Description:

Although never proven, a lot of people speculate that the smaller swallow on the left represents Louis and the larger swallow on the right represents Harry. This is because of the differences that the swallows have in their eyebrow shapes even though birds don't have eyebrows. The eyebrow shapes are very similar to Harry and Louis's.

The size difference is also something people attribute to them being representative of H&L

Added to timeline:

Date: