The two Wades: X-Men Origins and Deadpool 2016
Wade's birth shifted in time as effect of a time travel event that happened long before 'FIRST CLASS'. 'FIRST CLASS' is an effect of this time travel event too.
The time travel event of DOFP JUST affected 1973 and its following years/decades. Not before 1973, of course.
Wade 2016 is born in 1976, while in the original timeline (the first one) he was born in the fifties and was active in 1973 ("X-Men Origins: Wolverine")
The X-Men timeline was altered 2 times, not just one (DOFP).
FIRST CLASS was already a "divergence".
Everything is explained here:
THE X-MEN CINEMATIC TIMELINES
http://x-continuity.blogspot.com