So Tim starts stalking Batman and Robin and photographing them when he's like nine. Imagine little Timmy, looking at those pictures, amazed by his two favourite superhero, thinking that if anyone took pictures like this of his family, he''d love to have them because there's like one family picture and it's scary. So he decides to send them to the Wayne Manor, since the bats deserve to know how good they look and how awesome they are, and because it's always nice to have printed memories over the years. And maybe he also does it because he craves being aknowledge, and even if they don't know it's him, he'd like for the bats to appreciate his talent.
So little very smart Timmy, makes copy of the pictures and put them in an enveloppe, carefully not leaving any finger prints or proves (because if they find out it's him they'll tell his parents and he can't have anyone take this away), waits for the factor to pass by Drake Manor, silently drops the enveloppe in the man's bag while he's distracted, and watches the man go away toward Wayne Manor where the eneveloppe will be sent. There's nothing on the enveloppe except for Wayne Manor and nothing inside except for the pictures.
Naturally this break havoc in the batfamily because there's someone following them close enough to get those shots and knows their adress so their identity ?!? They wait for the other shoe to drop, for blackmail, ransom, but nothing come excepts for amazing clear shots every sunday that clearly shows admiration and worship. They look for this stalker during patrol, but since they can't catch him and nothing happens, Bruce put it at the back of his mind.
As the years go on, the pictures keep coming, always updated to the latest addition of the vigilantes family, although less often, maybe every two weeks/once per month. There're less pictures in the enveloppes after Tim joins, nothing too noticable, since Tim is not around as much (between patrol, college/WE, Teen Titan, not living at the manor...). He probably stops taking pictures around the time Damian arrives and the time stream happens, and since the enveloppe have been coming less and less, no one really notices.
A few years later, Duke moves in and decides to discover the manor. He ends up finding a box with the pictures and asks the others. Damian is as confused as him.
Two options from here, either Tim is exhausted (had been awake for 4 days, running on caffeine) when Duke asks; so he lets it slip it's him and chaos ensues, someone does the maths and Omg how old were you when you started ?? Then Stephanie asks him to take more, and Damian is like how preposterous there is non of the current Robin, when he just want to be included in the photos. Tim takes the cue and starts photographing them again, and realises how much he missed this.
Second option, Tim decides to mess with them and uses the opportunity as a stealth training, by following them and sending the pictures again. It's more difficult since he is busy. He has the hardest tim with Duke, because he patrols during the day and his powers don't help. It takes months for the batfam to realise it was him all this time.
