I've seen multiple different opinions on the whole plot twist with Squirrelflight and Leafpool and the three kits. I wanted to express my theory on both she-cats' side of the story leading to the whole kit chaos.
I like Squirrelflight, I really do. She was silly as an apprentice, but matured on the Journey to Midnight. When she first found out about Leafpool having kits with Crowfeather, she was pretty angry and shocked with dismay about her actions. Later on in the series, a Ashfur tried to kill the three kits in a fire, ending up in Squirrelflight revealing the truth. Because of her want to put her kin before her mate, it caused her to split up with Brambleclaw once he discovered her actions, though they later on became mates again. The Clan, especially Lionblaze, Jayfeather, and mostly Hollyleaf had resented Squirrelflight for her actions, but later on in the series, they kits have forgiven her. When her mate had forgiven her and had made her deputy, it could have represented Squirrelflight's nonstop loyalty, even in her darkest times during OotS.
In my eyes, Squirrelflight should have declined Leafpool's request, though it was her sister. Also, I think she shouldn't have told Brambleclaw, because if she did, it could result in Firestar and the rest of the Clan losing trust in him, as well as some of the other Clan cats. However, I'm glad that in the end of Bramblestar's Storm, they (SPOILER ALERT) have kits. (Hooray! Forget Jessy!)
To be honest, I never liked Leafpool once she was spending time with Crowfeather, but I did have a good side for Leafpaw. She had a great friendship with Sorreltail, and a nice bond with her mentor, Cinderpelt. After recieving her medicine cat name, Leafpool, she had grown more feelings for Crowfeather. Even when she had been an apprentice, Leafpool had actually been liking Crowfeather, and might have been hiding something about him. When Leafpool is plowed into and ends up having to hold onto a ledge, she is lucky to have Crowfeather help her, as he did not want to see his old love, Feathertail's death again through remembrance. Later on, in Twilight, Leafpool constantly keeps her mind on Crowfeather, causing her to mess up more on her medicine cat duties. During a gathering, Leafpool tries to see Crowfeather, only to be questioned by Cinderpelt about her forbidden love. In a dream, Feathertail visits Leafpool, talking about her love for Crowfeather. Soon enough, Leafpool meets Crowfeather and the duo admit their love for eachother. Because of this, Leafpool questions herself about her medicine cat position. When starting to meet in secret, Leafpool forgets one night, leaving an upset Crowfeather at the next gathering. When her sister catches her sneaking out, Leafpool persuades poor Squirrelflight into keeping her secret, later leading to kits. When a furious Cinderpelt discovers what Leafpool has been doing, she questions her and demands that she stops seeing Crowfeather. Leafpool, being a mouse-brain decides to refuse, resulting in Cinderpelt launching an attack on her. Suddenly, Leafpool flees for the Moonpool, where an annoying cliche stalker tells her to follow her heart. Of course, when she's told this, Leafpool decides to run away from the Clans with Crowfeather. When the two cats see Midnight, she warns that her kin is coming to attack the Clans and drive them out. After sleeping, Leafpool and Crowfeather realize they must go back to their Clans. Crowfeather comes with Leafpool to the ThunderClan camp, and assists in fighting the badgers. Because of the two of them running away, Cinderpelt dies, leaving Leafpool feel guilty about her mentor. When Leafpool had to watch her kits grow up in the paws of her sister and her mate, it left her devastated. After the secret was revealed, like Squirrelflight, Leafpool became depressed. With the Clan, especially her kits resenting her and her sister, Leafpool kept a deep state of depression. In the first book of OotS, she left her medicine cat position to become a warrior. However, at the end of The Last Hope, her kits had forgiven her, and Jayfeather allowed her to become a medicine cat with him again.
Phew! I had a lot more to write about Leafpool than I did Squirrelflight. I guess more story is for Leafpool, though, since it stated how they found out about the kits. Anyway, in conclusion, I think Leafpool should have listened to Cinderpelt, or at least try and talk to Sorreltail to get rid of her thoughts on Crowfeather. Instead, she was so obsessed with him, resulting in her depression later in the books, even having to know that Crowfeather chose another mate, Nightcloud, only to prove his loyalty to WindClan. Luckily, she never worried about Crowfeather in Bramblestar's Storm (At least I don't think, I completely forgot if I read it or not) and hopefully in the sixth series, she won't continue to worry about him.
Who I blame
Some of you might have found this obvious, some of you, maybe not. I don't mind if you don't find it obvious, but I blame Leafpool. She decided to meet up with Crowfeather, resulting in her having kits, making her sister raise the kits, making her sister lose her mate and have unnecessary hate from the Clan, depression, and having be demoted to a warrior (I think it was by her decision?) in The Fourth Apprentice. I say that Leafpool should have been punished severely by Firestar, but of course, Firestar can't do anything bad to his "precious daughter," and do only I think that Firestar might like Leafpool more than Squirrelflight just because she sometimes reminds him of... ugh... her? Anyway, I'm just glad that Leafpool has near lack/full lack of focus on Crowfeather, though I still think she's a pretty sorry excuse for a medicine cat/warrior. Please don't flame about opinions in the comments, and if you have a different opinion than me, just disagree lightly. Thank you.