
In ch9 you can see that granny says " YOU CAN'T BLAME HIM FOR BEING UNABLE TO FORM A DEEP CONNECTION WITH SOMEONE WHO ISN'T BLOOD-RELATED TO HIM." when they were talking about how seoin is spend time with jaewon only after he died so my point is, these guys are just step siblings and not twins or blood related
The mobs are just the sacrificial lamps that are gonna be beaten up to drain eve's power so Adam can recharge him and we get to see a good scene afterwards ლ(´ڡ`ლ)