Comment by Your mom- on Summoning a BL Fan to Another World - Chapter 3

@Your mom- They alternate, when one di** runs out of sperm they switch to the other one, each teste is dedicated to only one of the dicks.  They only use one at a time.  Apparently females can store the sperm in a pocket and can control when they want the sperm to fertilize her eggs,will get sperm from several males and can choose.  Male having two is to increace his chances by delivering multiple batches before they enter a refractory period.  It is literally to give them a second shot at insemination.

@Umberbone Don't know why I needed to know all that but, now I do.