We report on cooperative downconversion in Yb(3+)-RE(3+) (RE=Tm or Pr) codoped lanthanum borogermanate glasses (LBG), which are capable of splitting a visible photon absorbed by Tm(3+) or Pr(3+) ions into two near-infrared photons. The results indicate that Pr(3+)-Yb(3+) is a more efficient ion couple than Tm(3+)-Yb(3+) in terms of cooperative downconversion. We have obtained a highest quantum yield of 165% and 138% for Pr(3+)-Yb(3+) and Tm(3+)-Yb(3+) codoped LBG glasses under 468 nm excitation, respectively. However, ultraviolet light excitation to the charge transfer band of Yb(3+) does not result in quantum splitting as rapid relaxation from the charge transfer band to 4f(13) levels of Yb(3+) dominates.