I believe it has been established that JTK has only one nephew. If I'm wrong, I'll be sure to hear about it.
That's ambiguous. "What Are Little Girls Made Of?" stated that George Samuel "Sam" Kirk had three sons. "Operation -- Annihilate!" later claimed that Peter Kirk was Captain Kirk's only surviving relative. Some fans have resolved the contradiction by assuming the other two nephews died sometime in the few months between those episodes, or that they died in the parasite attack but somehow went unmentioned. But several previous tie-ins have ignored the line from OA and depicted Kirk's three nephews. Bottom line, it's a continuity error and there's no consensus on how to resolve it.