User blog comment:Xandermcc/The Barry paradox/@comment-3221148-20161007093318

Since Season 1, we've seen two types of time travel:

1) Superceding Your Own Past/Future Self: When Barry ran back in time to stop the destruction of Central and Star City, he -became- the Barry from the past, but with new memories, instead of running alongside him as a separate Barry.

2) Coexisting With Your Past/Future Self: Both when Barry traveled to 2000, and when he came to ask Wellsobard to assist him with the Speed Force formula, he coexisted with Barries from other time periods.

Since at both times Barry used the second method of time travel to get to 2000 (and the first one when getting to the Flashpoint, -becoming- the post-FP Barry, instead of going alongside him), young Barry would continue to exist separately, before getting supersided in 2016 of both Flashpoint-Timeline and NewThawne-Timeline by, er, "Our Barry".