In the first timeline(Terminator) kyle states he didnt see judgment day and that he,"grew up in the ruins". I believe Kyle was supposed to be 22 when sent back in time. The TDE was used as Skynet was being taken offline and the humans winning the war, this was in 2029. That would mean Kyle was born in 2007 in that timeline. John was born in 1985, thus Kyle would be 22 years younger than John. Keep in mind that JDay was in 1997 in that timeline. Seems a few items have shifted as a result of the various timelines.