I have heard this many times before. Is there scientific evidence for this fact? Or have any of you come across this in your lives?
There are studies that link cycling to Erectile Dysfunction. A quick Google will point you toward further reading. I'm afraid I don't know what the link is (or indeed whether there is a link) between ED and sperm count.
The link between cycling an ED is because of pressure exerted on parts of your body while riding. You therefore won't find it surprising to learn that people will suggest one saddle design over another, with this in mind. How much substance there is in any of this......it's all subjective.
I think that, in general, though, the health benefits of cycling (helping to prevent e.g. heart disease) are considered to outweigh the risks. ED, for example, is in most cases temporary and reversible.