I hold my stance on the fact that Maddie and Chim know about Buck's feelings for Eddie. You only have to rewatch 7x04 to realise how they know more than they let out. We all know how Maddie probably has an idea about how Buck feels from the "Boy Crush" comment back in season two. Well, the comment goes hand in hand with Chimney's : "I am your basketball beard. I feel so bonded" Specially when we take into account how he didn't know about how Tommy and Buck would end up being a thing. The comment is directed at Eddie's persona in relation to Buck's actions. And in both situations Buck doesn't deny it.
Not to mention, Buck can't help but overshare, and he is so transparent with Maddie that he straight up confessed to want Eddie's attention this whole time. Only to misdirect his feelings later on in the episode because it just made sense that he harbored those feeling for Tommy the gay guy, than Eddie the 'straight guy' who also happens to be his best friend. —Tommy also was the one who showed up at his doorsteps and kissed Buck. So at that time it only made sense for him that 'Oh, yeah. Maybe I do like this guy.' If you guys are wondering what moment I'm referring to (Buck confessing to wanting Eddie's attention) this happens after Buck tragically sprains Eddie's anckle. He visits Maddie at dispatch to say the following: "I was pissed, you know. seeing him and Tommy become such good friends after only two weeks. I felt left out, and I guess I was trying to get his attention." Referring to Eddie's, in no moment of their conversation do they insinuate Tommy being the one that Buck has his attention set on.
"But you don't like basketball."
"I know. But now he's going with Tommy, and he's got it circled."
Buck goes out of his way to include himself back in Eddie's life in places where he wasn't before because he feels that Tommy is taking all that empty spaces he's left. All his actions are directed towards Eddie, which he is conscious of at the beggining that it is about Eddie. But at some point in the episode his feelings get mismatched and the lines blurr between the two guys who are very similar to the other. Buck becomes an unreliable narrator of his own emotions, which happens somewhere between Maddie's and his conversation at her house and spraining Eddie's ankle.
"Acdording to Christopher he's already been over three times. Eddie just met the guy like two weeks ago. Christopher thinks he's 'so cool'." I would like for everyone to notice the emotional distance between Tommy and Buck from his point of view, seeing in his monologue as he refers to Tommy as 'this guy' or 'he'. Doesn't bother to clarify who he's talking about, and the impersonal reference alludes to how little Buck actually thinks of the guy up to that point (his real thoughts slipping through). The only time he refers to Tommy by name is when he's mentioning Eddie's basketball game to show where his distress falls.
"My point is he's made an impression in a very short time." Buck is so afraid of being replaced by some guy who happens to do something cool, he doesn't even realise how hypocrital it is for him to say certain things such as this one. Considering, as we all know, how quickly acquaintance Eddie and Buck became and how quick Christopher took a liking on him. It got me thinking about how Buck must've felt like he had to work for it (introducing Carla) to be let in, and how easy Tommy's got it. And that's when the thought of how easy he is to remplace starts to kick in, where the feelings start getting misplaced.
"Get this. He said he agreed Revenge of the Sith is superior to Return of the Jedi. I mean maybe it's just me butt I don't think you lie to a child just to ingratiate yourself." Once again he shows how worried he is about being replaced, specially in Christopher's life. Buck speaks like a protective mother. And once again we've got the indirect despectiva speech; Tommy isn't just Tommy he is some guy who is trying to make himself look cool to be liked and take his place.
I have to mention again the " But now he's going with Tommy, and he's got it circled." Because not only does Buck say it once, but twice during : " Eddie on his fridge has a day calendar. Under take-out menu Thursday,"B-B-P-U-W Backlash Tommy. And it's circled". "
It's always been about Eddie and how Buck feels that Tommy is taking his place. And then later when Tommy kisses him after he says he was trying to get his attention because yeah that makes sense because he can't possibly like Eddie romantically and so intensely. That is his best friend, his straight best friend at that. So he throws it at the nearest guy who is going to actually reciprocate–most likely. Its easier to convince himself to like Tommy, than it is to like Eddie and potentially ruin his friendship. (Let's not forget how even him being with Tommy later on was about Eddie and how he would react to Buck liking men.)
Back to Chim, there's also the scene when with Maddie they were discussing children right at the beggining of their relationships. They ask each other if they're the only people without kids that they know. It takes a second until they think of Buck. Because Buck is so integrated into the Diaz family, that it's impossible to think of him without Christopher tailing behind also.
Maddie and Chim absolutely know, or at least suspect about it.