Who knows? Maybe they didn't even meet at the docks. The MC found her brother and sehwa together after sending off the boy, no? Wouldn't that mean that they missed each other and the boy went first before her? That's a long time when you think about it if that is true, so it wouldn't be that absurd. Also, even if he did recognize her, he can't just go, "Hey! I'm your brother that you probably thought didn't survive! "
I think they are trying to keep it a secret, like Sehwa knowing her brother obviously and being able to recognize him, but acting like she doesn't. Most likely to keep their identity a secret for specific reasons.
wait now i’m a little confused..? aren’t sehwa and cheonho siblings?? like isn’t he that little boy from earlier chapters??? and he mentioned that sehwa told him herself about the pig dissection thingy so wouldn’t they have been able to recognize each other?? I mean even if it’s been a few years im pretty sure sehwa looks the exact same when she was younger cuz she was on the older side so cheonho should have been able to recognize her no?? like ur telling me if y saw ur sibling after not seeing them for a few years u wouldn’t be able to recognize them??? i highly doubt that…