fraternal twins are from the fertilization and implantation of two separate ovums eggs that develop into two babies. identical twins are when one fertilized ovum splits (for whatever reason) into two and creates two genetically-identical babies. twins do "run in familes". so there could be an increase in the frequency of twins on either side but mostly it would be the maternal (mother's) side;
how are twins formed? . i would like to know how identical twins and fraternal twins are formed. i would also like to know if the father being a twin affects anything. does it matter whether or not it runs in the mother's side or the father's side?