Since we know that they were headed to Tatooine at the beginning of A New Hope (confirmed by Bail Organa's conversation with Mon Mothma in Rogue One), did they know where he resided on Tatooine? The only way I could think of that Organa would know would be if Obi-Wan told him in Revenge of the Sith (didn't happen) or he knew where Owen and Beru Lars lived. If not, has it been established how they would have found him?
Bail was in the room when Yoda and Obi-Wan discussed splitting up the twins. He also dropped Obi-Wan off at Tatooine before delivering Padmé's body to her family on Naboo. He certainly knew that Obi-Wan would be in the near-vicinity of the Lars homestead and it's possible that he's been in contact with him more recently.
“Cliegg Lars still lives on Tatooine, I think-and Anakin’s stepbrother … Owen, that’s it, and his wife, Beru, still work the moisture farm outside Mos Eisley …”
“As close to kinfolk as the boy can come,” Yoda said approvingly. “But Tatooine, not like Alderaan it is-deep in the Outer Rim, a wild and dangerous planet.”
“Anakin survived it,” Obi-Wan said. “Luke can, too. And I can-well, I could take him there, and watch over him. Protect him from the worst of the planet’s dangers, until he can learn to protect himself.”