=fraternal twins(common type) w/c means two entirely different individuals.often they are a brother and sister.they develop from separate eggs that are fertilized simultaneously by different sperm..
=the other type of twins is the identical twins,on the other hand,are nearly the same person duplicated.they started life as a single fertilized egg.but after the first division,the two cells separated and started growth all over again.sometimes this happens several times,resulting in identical triplets,quadruplets or quintuplets..
(I have a diagram here of how an identical twins and fraternal twins formed..but I can't show it here..)
My grandmother was an identical twin (mothers side). The saying is that it skips a generation. I would have proved the theory because I had identical twins myself. (No fertility drugs) My grandmother stated that there were 4 sets of twins on her side of the family. According to the doctor who monitored my twins in the NICU unit, he stated that fraternal twins are hereditary. But, they are beginning to do studies suggesting that Identical twins might be hereditary also.
Twins are the result of one of two things happenings.
sometimes women release more than one egg during a cycle. If both get fertilized, the woman would have what they all fraternal (non-identical) twins.
sometimes one egg is fertilized and then cleaves, or splits into two separate embryos which would result in (identical) twins. Identical because the exam same genetic make up exists split into two.
Is it possible two have twins with two separate fathers.. Yes.. If a woman releases two eggs and has sex with two different men, one egg can be fertilized by one of the man's sperm and the other egg by the other man. Odds, not very big, but it could happen.
Sperm are viable for about 48 hours as is the egg that is released.
There is nothing one can do to conceive twins, I guess, you are trying to ask the biological reasons to conceive twins. There are several ways that lead to conceiving multiples or twins. Sometimes, multiple eggs are released from the ovaries. This is also called multiple ovulations. If both these eggs are fertilized, the female will be pregnant with fraternal twins. Another reason is when only one egg is released, but it splits in to two, identical twins are conceived in this case. There could be a case of three or more fertilized egg in which case the female will conceive triplets or even quadruplets.
Twins can come from various places. There are two types of twins. Identical twins occur when a single fertilized egg splits into two fetuses. This is usually genetic, look at the family history. The other type is fraternal twins, and this occurs when 2 separate eggs get fertilized. While there can also be a genetic predisposition for fraternal twins, they can also occur when fertility drugs are used, causing the woman to release more eggs than usual, or with in vitro-fertilizations where several fertilized eggs are implanted.
