@Riot; Can I get some Clarification on Knight's Vow?

I GOTCHU FAM UNIQUE Passive: If your Partner is nearby, heal for 12% of the damage your Partner deals to champions and redirect 12% of the damage your Partner takes from champions to you as true damage (healing and damage redirection are reduced by 50% if you are ranged). (Champions can only be linked by one Knight’s Vow at a time.)

Specifically the last sentence. Does this imply that two champions with Knight's Vow cannot link with the same allied champion, or that two champions with Knight's Vow cannot link with each other (or both)?

It's hard to tell just by the description given here, it's a bit vague.