Edward and Anthony are for sure close in age. They were debutantes together with Gerald and Aileen.
It's more likely that Alfred, in his old age, knocked up some young girl to conceive Anthony. But lets say Alfred was in his early 20s when the Mirror's house got taken over. add the 50+ years, since thats how long it took for Kate to finally be born from her mothers shadow stasis, and you get an old guy who was in his 70s when he sired Anthony. Major ick. Anthony is biologically OLDER than Kate (he was probably born a few years before she officially came out), however chronologically he was (at least) the second child to be conceived by Alfred. I say at least because I suspect there are more half-siblings (it just makes sense if they're trying to keep their family numbers going to do a take over one day) but currently these hypothetical siblings don't matter. What matters is, Kate is chronologically and biologically ~13yo. Even if you count her being inside her mom's womb as part of her chronological age, it doesn't change the fact that Kate is ~13yo. That's how she biologically and chronologically aged once she was actually born. She's not a child with an adult mind. She IS a child.
BUT what makes this intriguing is how Anthony knows this at all. Like ok, his family are also the true heirs of Mirrors house and they've been bidding their time. But how were they certain KATE was Catherine's daughter by Alfred. That's still a leap in logic. Cuz for all Alfred's faction knew, Catherine escaped and died with child. Or if the child was born, said child would be in her 50s. This is where our theorizing about the right hand man of Great Grandfather comes in, the enigmatic Joseph who up to this point had not been a real player in the story UNTIL he grabbed the suitcase of clothes (which would be recognizable to someone from the og Mirrors house that was close to Catherine) that Edward found, and then name dropped Catherine himself. So I'm thinking Anthony had been able to hide as well as he did bc he did have help from the adult wing through Joseph. Otherwise, how would Anthony be so sure Kate is Catherine's daughter. The only tell would have been the clothes and the nickname "Kate" would have confirmed it. But then WHO is Joseph? Alfred's brother?? Catherine's brother?? The plot thickens.
I'm just really excited because this makes sense when looking back at Anthony's previous actions. His "golden age" for the Children's wing with Christopher was his long game and it worked especially well with Lewis and ofc Barbara. I'm still curious about his relationship with the original Christopher behind the scenes. Did he convince Christopher, or was it like Sara and Mia's relationship. I laughed when Anthony basically said "yeah i know how to get Edward to do exactly what I want." He WANTS Edward to figure out it's Anthony; he said he left Edward a hint, which is interesting. Specifically also because of the way Anthony said he left the mangled bodies inside the unification chamber WERE the hint for Edward. I wonder who Anthony murdered in the past to pull off his own "death" lol. Everyday we get closer to the Edward Group/Anthony reunion and I want to see if there's any drama there. The fact that Anthony WANTS Edward to figure it out at all makes me wonder what kind of rivals they were. What was their history....
Just questions I have now: In the case that Alfred and co. sired more kids over the years, did he and his group send them to the Shadows house on purpose every few decades to try to gather intel on the Shadows house? Are there more family members among the adult wing who are waiting for Anthony's signal? Although they wouldn't have been able to leave at first, recall that some adult shadows DO get to live outside with regular humans. The human wouldn't have made it but a well convinced shadow might have reported back to the family upon making it outside. I dunno, I just wonder how involved this operation was over the decades. Anthony played the long game well but he had to learn to do all that carefully from somewhere. He had orders.