The Flash Cobalt Blue story, starts with V2 #143
The plot is stupid, but consecutively interesting
Barry Allen had a twin, his twin was adopted by Thawnes
Malcolm found Barry is his brother, and he started a family feud over it, but his last name is Thawne
Every Thawne finding the Cobalt Blue gem fights a Flash
One of the Thawne's is Eobard Thawne
So that makes Eobard Thawne a distant nephew of Barry Allen, the second Flash
There is an Allen in the time period of Thawne/Reverse Flash/Professor Zoom, he's a cop, and his father gained the Cobalt blue gem
The funny thing is, this is the 25th century, and Barry retired in the 30th century, that's when his twins and grandchildren were born, and stayed, until Bart/Impulse/Kid Flash jumped back with his grandma to the 20th century
Could the Allen's in the 25th century be descendants of Bart Allen?