For my ally is the Force. And a powerful ally it is.
Obi-Wan had meditated long and hard on why he'd been brought to Vallo but the Force remained stubbornly silent on the matter. However, Luke's arrival seemed a sign.
The youner man shone brightly in the Force, but his presence was raw. Untrained. That he was from the future made Obi-Wan certain Luke was Anakin's son. He hadn't been blind to the connection between his former apprentice and Senator Amidala so it was no surprise that the two had procreated. What was a shock was everything else. The things Obi-Wan had said he didn't want to know but was able to infer from what Luke had mentioned.
He tried not to think about what all that meant, and 'focus on the here and now' as Qui-Gon had always reminded him. There was nothing he could do here about what had happened in Luke's past. But he could prepare the younger man for the future.