Your cousin has four fewer hops than you which basically means that, right out of the gate, his packets are 20% less interfered with.
There really isn't a whole lot that you can do about it unless you started establishing your own routing tables in house and directing your traffic through different devices but this would be an extreme pain to manage at best and there is no guarantee that you wouldn't find out that the bottleneck still stands between you and a main backbone before your route changes would make a difference.
In short, I agree with TM in that there really isn't a whole lot you can do; it comes down to the traffic, quality, and routing protocols at work on the network devices used by your ISP, then their ISP, then their ISP, and they'll tell two people, and they'll tell two people, and so on, and so on.... Maybe find a different shard or let go of playing a dueling mage if you do
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