the way that the whole thing works is that there's a gem / crystal in a chandelier on the ceiling in the grand foyer. and it radiates this sort of...ray, idk. and it sort of alters the women's dna to respond to its rays. it prolongs their growth period so they become much taller than they would be otherwise?
and this is why coraline is shorter than her sisters - the divorce between her parents stunted her growth by having a shorter period of exposure to the crystal? jade spent a lot of time at home, so she grew taller than her sisters/mom?
but aurel had some mutation/alteration that caused his body to start responding to the crystal much stronger? and start to grow even when he's matured? everything feels like a stretch and nothing is remotely plausible. why.