This isn't possible with Hacker News since the voters are not public.
I had done brief analysis that shows that the (YC X) submissions do receive more upvotes on average. Which is hard to attribute to a voting ring specifically.
I often feel more inclined to upvote them because, in the end, YC created this community and I feel their incubees deserve a bit of that reflected glory.
It's my way of saying thanks, and I suspect other people's too.
I had done brief analysis that shows that the (YC X) submissions do receive more upvotes on average. Which is hard to attribute to a voting ring specifically.