The pumps might be the same in amp/volt and make (that is, they use the same motor) but one of them might be a pressure pump (high pressure with less flow) and the other might be a high flow pump (high flow with less pressure).
Take a look at the impellers of these pumps if no flow/pressure chart is available.
Assuming both are pressure pumps (or both are high flow pumps), then take a look at the geometry of the pipes feeding and exiting the pumps, until the point where these pipes meet, you should see a mirror image, leading to a Y connector (top of Y comes from each pump, bottom of Y is combined exit).
Even better, post some pics.