Gosho and the captions
Might he be lying?
The new brother is younger than Akai, so we can assume he is at least 20 (oldest than Sera), but he can't be 27 or more: Akai should be 27 if we assume that Okiya's age here (
File 623) is reliable; and it's almost certain that Okiya is Akai after the Mystery Train series. Still, Gosho sometimes
lied in his captions: during the Detective Koushien case, Koshimizu Natsuki's caption states she is 18 (
File 563), while it will be later revealed she is indeed older. If Akai is disgiusing as a student, then it's no surprise his caption would say he is 27, a natural age for someone who wants to get a degree in engineering. Still, if he is really Akai he might be older as Natsuki was. This means that people like Shuukichi Haneda, who is 28 if I'm not mistaken, shouldn't be ruled out because if Akai were 30 or so he would really be younger than him. Then, the maximum age of the second-oldest brother increases up to 28-32 or something like this.
Blushing is the way
Sera's second-oldest brother and his behaviour
Looks like he is a white-skinned, right-handed guy. There are a lot of characters who matches with this description, but at the very least we can rule out Amuro (not white-skinned) and Okiya/Akai (not right-handed). Still... did anyone notice how Sera blushes when her brother asks her who she's talking about and when she takes a photo of Conan to send it to him? It would seem her second-oldest brother is an overly protective guy who is jealous of his own sister and Sera blushes thinking her brother's angry text (
"Who is "he"? I'd like an explanation!") may be a result of him thinking she's dating someone who's skilled at deductions. If that's true, I should think of a person who could likely act like this...
The magic of... being siblings?
Sera and the Kuroba Family
Then, the P.S.: Sera was probably looking for some "wizard" and had told her brother so: thus he asks her if she found this wizard, and she mentally answers "yes"... since she's now realizing the wizard she'd been looking for was Conan? There are a lot of hints pointing towards magic, tricks, wizards... Kaito Kid involved? Well... I don't really know. But seeing how the next case is about the white magician, seeing how Kaito Kid recently was involved in BO plot, seeing how Sera herself already met Kid... I wouldn't rule this out yet. After all, doesn't the Phantom Lady resemble Sera? The way her hair falls by the side of her cheeks (
MK V5-2) really reminds me of Sera's hair. It's just that Sera's hair is black, but the black color is expressed through a dominant genes and thus she might have taken the black hair from her father. This doesn't mean she is Kaito's sister or whatsoever, after all Kaito Kid doesn't even know she was a female... I was just sharing my thoughts. Plus... I think the Phantom Lady's breasts are kind of well-developed; and Sera said her mother's breasts are huge (
File 771), and it is implied that Ran knows Sera's mother... and that's it, I wouldn't find it strange if she and the Phantom Lady did meet each other somewhere in the past.