Jason Yan's company, Disqus, was funded by YC in the summer 2007 funding round.
The other connection says:
Jason and Ethan are startup founders, and know each other through Y Combinator.
The other connection says:
Jason is a cofounder of Disqus, a YC funded startup.
The other connection says:
Daniel met Jason at Y Combinator in the summer of 2007.
Jason is a founding partner of Disqus, a commenting system for your blog or webpage.