'This Is Us': 5 Game-Changing Reveals From the Season 4 Finale (PHOTOS)

Meaghan Darwish

[Warning: This gallery contains MAJOR spoilers for Season 4, Episode 18 of This Is Us, "Strangers: Part Two."]

This Is Us served up some seriously game-changing details in the Season 4 finale's final moments, from new family members to possible relationships. Needless to say, it was hard to keep jaws from hitting the floor as reveals came one after another.

'This Is Us': Will the Clinical Trial Work? Why It May Not Help Rebecca

'This Is Us': Will the Clinical Trial Work? Why It May Not Help Rebecca

Rebecca's future has been teased various times throughout Season 4, could those flash forwards hold answers?

Whether it was Kevin's (Justin Hartley) twins or Jack Damon's (Blake Stadnik) sister, there wasn't a twist that didn't leave viewers thinking long after the credits rolled.

In the gallery above, we're breaking down the finale's biggest surprises, including those twins, the sister, and Uncle Nicky's wedding ring. Click through for some possible clarity, theories and more.

This Is Us, Season 5, TBA, NBC