Who is responsible for the delay in corn supplies?   Dumnorix
Who is he related to?   He is the brother of Divitiacus.
What is his postition?   Divitiacus is one of the Aedui chiefs.

Caesar made a tactical decision to follow the Helvetii and, by force, to stop their migration through Gaul   In my opinion, this decision could have been a disaster for the Roman army, who might have starved, but he played his hand well, by giving the chiefs of the Aedui the impression they were among his inner circle, embracing them and seeming to take them into his confidence.   Though he claims to have genuine feelings for some of them, he characterizes them as children, who cry at the drop of a hat, which I find someone incredible.

Having left the area of the River Soane for the pursuit, and with it, the only sure means of obtaining corn from the vessels he'd ordered to follow his company up the river, Caesar presses Liscus, the Aedui Vergobretus (elected chief magistrate), for delivery of the Aedui crops under their prior commitment.   But Liscus continues to stall.

Finally, after a reprimand, Liscus comes clean with the information that the brother of the Aedui chief, Divitiacus, is responsible for the delay in the corn supplies. Dumnorix is the brother's name. Having gained wealth and with it a measure of independent power from brokering customs and taxes, and through a series of arranged marriages between his family members and other tribes, he styles himself the future leader of a united Gaul. But, Caesar is too clever for him, it seems, and Dumnorix is put under surveillance.   The story continues . . . .

The Gallic Wars - Book I, Chapters 16-20

Am I right?   Did I get the bonus? *S*