Yes.
No. Only a heifer calf twinned to a bull calf will be infertile, not twin heifer calves.
Yes, they can and have in the past.
There are so many different things, and something that will make one person infertile will not affect another. Some people are born infertile and often there is no apparent reason.
No. If a woman is infertile, sperm will have no effect on her. Infertile means she cannot get pregnant.
Infertile also means unproductive or barren.
No, not all female werewolves in Twilight are infertile. In the Twilight series, it is mentioned that female werewolves may have trouble conceiving due to the physiological changes they undergo, but it is not a definitive rule that all female werewolves are infertile.
Yes, I'm afraid so, anyone can be infertile.
Fertile will support plant life, infertile will struggle.
Squirrelflight is not infertile. She and Bramblestar have kits together in the Warrior Cats series.
Infertile soil or land can be solved through the practice of bush fallowing.
They should've dropped before the bull calf was born. If not then you have a crypto bull on your hands, and an infertile one at that.