So we've got this pretty high-ranking rebel leader, Qu Rahn, who happens to be a Jedi Master of the old Jedi Order. This isn't some guy who has abandoned the Jedi code in favor of a normal rebellious life. His status as a Jedi is well known to Rebels like Mon Mothma and Morgan Katarn, and he was a Rebel leader at least from 0-5 ABY, when he was killed by Jerec. Then we've got this new kid, Luke Skywalker. Killed the Death Star with an impossible move, and he's throwing around words like "Jedi" from the very beginning. He's the poster boy for the Rebellion. Within the first year, it seems everyone's heard of the new hotshot Jedi pilot. And he's got the Chosen One's last name. So why did Rahn never seek this kid out? They were Rebels together for five years, and Luke doesn't even know about Rahn until the he's secretly dead!
I wasn't aware Rahn was a Rebel leader. Where did you get that from? The only person he knew from the Rebellion, IIRC, was Morgan. Edit: Still, it seems as though he kept tabs on the Rebellion's activities, so your point stands. Maybe Yoda told him to leave the kid well alone on Rahn's visit to him?
Simple answer: The Galaxy is a big place, and Qu Rahn had other things to do and/or the "will of the Force" did note bade him to seek Luke out.
Well, if you wanted to fanfic it out. Luke Skywalker: So, you're a Jedi Knight? Rahn: Yes. Luke Skywalker: I'm interested in becoming one, mostly because of my father. Rahn: :twitch: Luke Skywalker: I want to be just like him. Rahn: :twitch: Luke Skywalker: So can you teach me the Jedi Way? Rahn: No. Luke Skywalker: But... Rahn: No.
After a second look, I may have overstated Rahn's involvement with the Rebellion, though he was leading a party of Rebels when he was captured by Jerec, and Mon Mothma definitely knew him. That's my current assumption. Yoda realized the New Jedi Order had to be free of the baggage of the Old, so he asked Rahn to avoid the Jedi twins who would hopefully save the galaxy.
Counterpoint, also, Rahn REALLY hated Anakin Skywalker too with a most Un-Jedi like disdain. Also, Yoda's favoritism of Luke aside, Rahn started training Kyle Katarn independently of Yoda's will.
Rahn was made a "Master" by Yoda sometime after Order 66. There are conflicting sources on his earlier life; the series of Dark Forces articles on the WOTC page stated he was only a youngling, but the online HNN articles had him as a Jedi Knight circa 22 BBY. It was also said that he knew Mon Mothma personally in the Soldier For the Empire, so he may have been considered a "special resource"; Mon Mothma certainly would know what would happen to any former Jedi if their presence became known and wouldn't risk sharing that information if there was a chance he would've been caught.
I think the WOTC Dark Forces article is simply a little too abrupt and poorly parsed in its biography of Rahn, and isn't actually claiming that he was a youngling at the time of Order 66, but rather that he was one "years earlier."
Yoda never knew about Kyle Katarn, nor his father. Rahn saw a special relationship between Kyle and the Force, so naturally, he was drawn to help Kyle develop his potential.
I think if Rahn had survived any longer then he did, there could be no excuse for him and Luke not meeting. As it stands...not only did they have a galaxy between them...but an Empire with an edict to destroy them both. If Qu Rahn was aware of Luke...he did well to avoid giving the Imperials the chance to catch them both together. Plus, his mission was the Valley...it took prominence over everything else. And if Luke knew he'd either: 1) want to quest off with Qu Rahn...taking him away from more important events where he'd be needed. 2) He'd try to convince Rahn that other matters took precedent over the Valley. 3) Kyle may have killed Luke for questioning Rahn. As it stands...the whole "last of the Jedi" thing has been so frauded that just asking this question about Qu Rahn is pretty silly. Let's just say the force told the rest of the slacker Jedi of the dead order to leave the boy alone...he was going to save the galaxy.