So does Vanya. I think Ellen Page could almost pull off being a pre teen if she wanted to.
And NewBen has a (faint) mustache. So you know he's going to be a douche.
I think he's 16, so they either have to really age up Five and replace him with an older actor, or incorporate a time jump so the character catches up with the actor's age.
Five said he didn't expect to be 13 when he reappeared in 2019. I could accept a handwave that time travel, at least he way Five does it, has unpredictable effects.
But the nannies were someone new each time and then they were replaced promptly. And she was not punished for killing them, although all the children were punished harshly from a very young age. She had no reason to think they were people any more than her dolls.
If the children were allowed dolls and toys.
Either they have the same father, or they were conceived parthenogenically, in which case we would expect more females. (Only more because there are more combinations than XX and XY).
But if parthenogenesis is involved, with some added mutations, then they are not related genetically at all, but only have their mother's genes.
I'm probably thinking of Orphan Black here. And it is interesting that Allison was able to bear a child.