V1 is related to runway performance (length, condition, wind etc) for a given weight while Vr and V2 are related to the airplane weight alone.
The relationship between V1 and V2 is usually expressed as a ratio. If a turbo prop it might be a ratio of 1.0 thus V1 = Vr, or it might be .85 in a jet thus V1 would be 85% of the Vr speed.