Cisplatin and Diakinesis did end up having a fifth child, a boy I renamed Trophoblast. Like most of his older siblings, he already had likes so I didn't use the encyclopedia with him either. Cisplatin reached the top of his career, becoming the first peep in that family to master a kitchen career, getting me trophy #84.
Peptide and Blastocyst have both left for college at this point. Diakinesis is 56 (and only on level 5 of her career, though close to a promotion now), Cisplatin is 54, Lysine and Polymerase are 16 and Trophoblast is 12. I'm planning on having Blastocyst inherit the house after Cisplatin and Diakinesis eventually die.