Dizygotic, meaning that they developed from two different eggs fertilized by two different sperm cells, while identical twins are. Hysterical narcissist, austen is transposing one of the enduring clichés of romance plots. Beautiful twin sisters vicki and valerie darger are so close they even share their husband. Two separate babies with no more in common than siblings born at different times are formed. Fraternal twins occur when two separate eggs are fertilized by two separate sperm.