Many things Diabetes, Ciggarettes, Alcohol, The Wrong Credentials(boxers or Tidy whities), depression, or he's just broken.

Tightie Whities (scrotums too warm)DehydrationGeneticMumps as a child/teen.VasectomyTraumaSTD'sHave him see a urologist, spit in a cup, get a count, then ask the urologist why the count is low, if it is. Otherwise Yahoo! or Google "low sperm count".

being sick, drugs, alcohol or possibly genetics.

Not wearing boxers. Heat kills sperm and lowers sperm count.

-new study shows that the diet of the mom during her pregnancy could affect the sperm count of her child.-too much masturbation/ejaculating frequently-drug

A man's body produces sperm on a daily basis. It is either poor diet, smoking pot on a daily basis, the twins are to hot all the time or that is just normal for his body.