The children voices for NVDA can be tryed for free for 15 days see link below. No these voices aren't Kelly and Nelly and there are more than just US and UK English. As for the real names behind these voices let's hope they stay secret for safety reasons. Josh and Ella are the girl and boy US voices, Harry and Rosie are the Brittish english voices, Liam and Oliviaare are the Australian voices, Emilio and Valeria are the Bilingual US english and US Spanish voices, Jonas and Lea are the German voices. There is also Scot a US teenager voice. Also there are 2 new Swedish voices that have not been released yet Filip and Freja. All the voices except for Filip and Freja can be brought for Text Aloud but they will only work with text aloud. You can buy them for NVDA for like 100 Euro I think it is however the Swedish and German voices are not available on NVDA. Also at this time the prerecorded sounds the voices can do do not yet work with NVDA. You can try these voices out for yourself using the Acapela demo found here.
http://www.acapela-group.com/
NVDA Voices can be brought or tryed for 15 days here.
http://www.acapela-nvda.com/download/
Here's a link to the Text Aloud ones but honistly it's cheaper to get them for NVDA since each voice is about 45 dollars.
http://sites.fastspring.com/nextup/prod … rensvoices
Kingdom of Loathing name JB77