The Trouble with Vulcan-Human Hybrids

A story in which Spock and Kirk meet their future children when accidental time travel happens. Future Spock and Kirk have twin children, a son and daughter, who each take after their parents in unique ways. After a bit of an accident, the two children are thrown into an Enterprise where Dad and Father are still only coworkers, learning how to get along with each other.
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“He’s got hobgoblin blood, too.” McCoy shook a vial of green blood for them to see.
Kirk had finally set the PADD down, at the foot of Spock’s hospital bed. “So he’s half me and half Vulcan?” Kirk’s eyes flicked over Spock’s face. “Is this a joke?”
“I was going to ask you that,” McCoy shrugged at Jim. “You have yourself here a Vulcan-Human hybrid...a Vulcan-Kirk hybrid.”