Okay so there's a few cats in the series who have almost become mates, but another cat comes in last second. Some examples include:
Dustpelt and Sandstorm. They were really close as apprentices, and I bet that if Rusty had never stalked that mouse in the woods, their kits would be warriors fighting for the Clan. Firestar joined the Clans, Sandstorm realized she liked him, they became mates instead, Dustpelt ended up with Ferncloud.
Squirrelflight and Ashfur. You all know the story. Squirrel and Bramble break up, Ash comes in, Squirrel goes back to Bramble because she's the biggest drama queen the Clans have ever seen, ect ect.
Another example, though kind of fuzzy, is Dovewing/Tigerheart or Dovewing/Bumblestripe. So, with the new super edition coming out, it's largely hinted that it's gonna involve some Tiger/Dove romance. Dove and Bumble were mates, and of course she broke up with him because she "couldn't see him as more than a friend" but you know, that's probably a lie as all she thinks about when it's her PoV is Tigerheart.
Bramblestar and Jessy. I think they would've been really cute together, but back to Squirrel's land of drama, yadda yadda yadda, Bramble and Squirrel always end up back together because love is powerful or something, I guess. I think it would have been interesting to eventually see them part ways and take new mates.
So, what do you guys think would've happened if these interrupted relationships would've carried out? (Like if Alderheart had never been born since SqurrielxBramble didn't happen, how would that effect the current plot?) I think about these things a lot, and I wanted to see other people's opinions on it.