Bioman- Their ancestors were scattered with bio particles thus the descendants were picked up to become the new Biomen. It was their destiny.
Turborangers- The rangers were exposed to fairy energies when they were young causing them to become Turborangers in the future.
Fivemen- They were destined based on their parentage. That's just my opinion.
Dairangers- They were destined from their lineage.
Kakurangers- I think they are destined because they are descendants of ninjas.
Gingamen- Being descendants of the Gingamen made then Gingamen.
Gogo V- Compared to Lightspeed Rescue, the Sentai counterpart had them apparently destined because of their father's pre-planned decision.
Gaoranger- They were destined to be Gaorangers probably based on lineage.
Abarangers- It was their destiny to become Abarangers because of the Dino Guts.
Magirangers- Apparently, it's destiny by lineage compared to the Fiveman and Gogo V sibling teams.
Shinkengers- Except for Genta (not pictured), they were destined to be samurai even for the shadow warrior Takeru Shiba because of their lineage. Well Takeru Shiba's father (whatever his name was), was also serving the Shiba house so that may count.