The quantity as well as quality of sperm cells that men produce varies widely. In general, men may produce between 2ml and 5ml of semen each time they ejaculate, and that each millilitre may contain from 10 million to 300 million sperm cells. It means a fertile man may produce between 20 million and 1500 million sperm cells in total, though the majority produce between 40 and 60 million sperm cells per millilitre. Same verity is reflected in quality too. Not all human sperm cells look the same. Some have two heads or no heads, some have huge heads, some have small tails or no tails, others may be bent at right angles, or have spiral tails. Many of the unusual ones are probably not fertile at all.
No, which is why each conception produces a different result. Even in the case of multiple identical births (twins, triplets, quadruplets, etc.), if I'm not mistaken, it's a single sperm cell that fertilizes the egg, and as it splits, it forms multiple feti. Fraternal twins occur when a separate sperm cell fertilizes a separate egg. ~
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