in this universe. dbz and dxd are in the same universe. the difference is that Broly was sent to Earth instead Vampa when he was child. when broly first landed on Earth at age 2 in a space pod, Azazel was the first person to encounter Broly. however instead of killing Broly. Azazel decided to take Broly into his home as his own son, over time. Azazel figures out that Broly was a Saiyan. so Azazel kept Broly's race a secret. now at age 17 Broly started his first day at Kuoh Acadmey