Those two are way too far back in time to be meaningful. Don't forget in the AOL most Aiel with the ability joined the AS and were likely removed from the Aiel gene pool, though we don't know for sure If Aiel and AS ever married together.

In any case, it suggest the ability was initially rare and it could,have taken the Breaking and generations before it became more frequent among Aiel. It's perfectly possible Janduin had the latent ability but not the spark. All he needed was his two parents passing to him the recessive gene. It doesn't mean the ability has to go far back in his line. He didn't even needed that, both Tigraine and Janduin only needed to carry the gene for the ability as a recessive one, and Rand inherited the recessive pair and thus can channel.. Don't forget about hidden channelers. Tigraine's female line would likely have trained in the Tower and been found, but her paternal line, or her mother's paternal line, could hide many latent male channelers. Same for Janduin. He may have a WO not far in his ancestry or a latent male channeler. All that matters is that rand inherited the recessive genes from both side to,develop the ability. It means all his children from Aviendah and Elayne will be channelers as all the parents have a pair of recessive genes to pass and none has a dominant to block the ability. The ability can vanish in a blink in the next generation, all it takes is one parent having a pair of dominant or an heterogenous pair and passing the dominant.