Here's an update - finally - purely because this chapter popped into my head, fully formed, ala Athena. No Bones just yet but the boys are getting older; they still have to survive puberty to get to Starfleet.
The letter - and it sits there in his 'Conversations' folder, looking innocuous and innocent - Spock hardly believes, at first. He taps on it, opening it cautiously, unsure if perhaps it is some kind of prank; he hasn't heard from his pen-pal in years, after all. Surely he'd grown bored, or had forgotten about him.
But that was not the case. No, what Spock read - three times, before it even really sunk in - was something much, much worse. There wasn't much information available about Tarsus IV - but everything that was known about the planet was terrible, consuming in its' awfulness. There were said to be only a handful of survivors - a handful, from a planet that had been brimming with humanoid life mere months before.
It takes the teenage Vulcan a few days to reply; the first night, he cannot sleep more than an hour at a time, the images of the horrors Tarsus IV went through - the media having plastered them on every newsreel, forum, and social site available - always at the edges of his mind. The second day he goes through the motions of home and school mechanically, evading the questions his mother asks with feigned ignorance, the night spent looking up every statistic he can think of.
He doesn't pay attention in class on the third day, writing and re-writing his letter. He even taps at the screen through dinner, to the slight frown of his father and the heavier worry of his mother. Only I-Chaya does not change expression, instead happier that he is getting more scraps than usual from the dinner table.
Eventually, because he does not want the other boy to think he has ignored his letter, Spocks taps 'Send', and lays in bed, the glow of his PADD a companion to the whirling thoughts in his head.
Penpal,
Our sorrows for your sorrows. I have heard of what transpired on that planet, and...