Though the meaning behind the tribute is pretty clear, fans are still in the dark about what the digits might stand for, but there's plenty of speculation in the comments section of the photo. The most likely theory is that it's related to the siblings' dates of birth — Presley's is July 2, 1999, and Kaia's is September 3, 2001 — which would make sense, considering birth-year tattoos are JonBoy's personal specialty . Regardless of the significance of the numbers, Presley officially just landed the role of best big brother of all time. Now, all that's left for Kaia to do is return the favor... or maybe she already has?