I love tattoos. I have an affinity and obsession with them. So.
Bradley. Has tattoos of his dad's dogtags. Because Mav was an idiot that threw the actual ones away but Bradley wants to keep his father close so he gets the dog tags tattooed on himself the day he turns 16. Because his mother's also dying and he wants her to know that in her absence he won't forget Goose or her and that he'll always be both their sons even if he forgets parts of them in the long run. He doesn't mention that he's forgotten most things about his dad already because his mother and Mav know and that's why they keep telling Bradley stories. To keep him alive.
The day he turned up at his mom's bedside with the tattoo freshly done and wrapped on his arm, his mother cries and also hugs him and hold on to him. Mav just sits in the silence watching his best friend's family and vowing to himself to protect them with everything he has.
He doesn't mention that he had a goose tattooed on his hip for years. He doesn't mention how Goose had once joked about getting matching tattoos with him so that everyone would know which pilot/Rio they belong to in case they ever get separated.
Weeks later when they bury another of Bradley's parents, Bradley adds a ring to the dog tags on his arm. There's a miniature script running next to it saying 'show me the way home honey'.
Mav doesn't let anyone know but a Hen tattoo joins his goose one.
(I have more I'll be back soon with rest)