I don't know if they're identical twins and MC is just an idiot or if they're fraternal twins that are of the same sex and so they look similar...
Also, assuming the father is there, hopefully he'll sort out the crazy...But then again, there remains the possibility he is also like this. I found how insane they are funny, in a sick kinda way, but holy hell does this explain a lot about FMC. I'm worried MC is gonna get sexually assaulted by her family though. They seem to be on the hunt...