Charlie Casey, or the youtuber charlieskies, became friends with Phil sometime in mid to late 2008. The oldest currently surviving tweet that references the two of them talking is a tweet from Phil dated 4 Nov 2008. ("Having a surreal convo with Charlie!!! O_O")
Emma Blackery briefly mentions Charlie and his relationship with Dan and Phil twice in 2016:
Her support of the charlieskies twitter bullying on her main channel (11:49):
And in July 2016 (the 26th) she was invited to speak in Shane Dawson's podcast and said Dan and Phil "hate" Charlie now:"I used to laugh along with a friend who was really nasty to Dan and Phil. I used to think it was fun to sort of show tweets of support to that and, and feed off that drama, that's what I used to do, I used to be like that. And looking at it now I'm not even that person now, it's weird that that's me I don't, I don't think in those negative ways anymore."
transcribing creds to fancybum!Shane: So who have you had beef with?
Emma: This is the thing, I don't like saying because every time I even say their names, their massive group of fans-- massive group of fans-- of these two Youtubers--
Shane: Ohhh-- OHHH!
Emma: They hate me, they don't like me, their fans. At all.
Shane: Ok, I won't say their names.
Emma: Some of them do. It's a vocal minority that really don't like me. I was a massive fangirl of these two Youtubers who were very big in the UK, a massive fangirl back in 2012-13. They're one of the reasons that I started, I think they're great people. Um. But I was very over-the-top with my fangirliness; I had the shirts, I'd make all the references, I was basically cringe-worthy. It was cringetastic. And I really wanted to be friends with them, and I was trying to talk to them, I'd email them to collab, I had like 10K subscribers, right. I was very naive and stuff, and like obviously they would get so many emails, they didn't reply or anything. But I took it personally, and this was years ago. I took it personally, like "Wow, they're shading me. They don't like me." And I was friends with someone who-- uhh... was... friends with them a long time ago who they now hate so then lots of drama started with that. And ever since--