i guess this would be a genetics question.

[SnakeDoctor]

ok, say i had a twin brother. we both had a child with twin sisters...is it possible that our children would come out looking the same?

[Awakened_Mind]

That's a very interesting question.

-AM

[Bird]

  Very unlikely. Even all the children you have with one women will look different, the genes getting a new mix. But an interesting question.
I know two women who look like identical twins, but they are only sisters. Nothing is impossible, this thing could happen.

[SnakeDoctor]

i was thinking about that on my way to get my check from work.

[Awakened_Mind]

Does opposite have an opposite? Or is it some higher concept used to explain the relationship between two lower ones?

-AM

[volcomstone]

  Meiosis is the splitting of the genome into two (haploid) cells (sperm or ovum).  This process is a random selection of half of the genes. 

  However dominant genes shared between the two of you (your brother and you) and your wifes sister will most likely be expressed in the children , but its a random assortment as well, depending on mendelian genetics.

       Sooooo if you have brown hair and brown eyes, and your wife has brown hair and brown eyes, then its most likely that you'll have brown eyes, but theirs a  1/4 chance that they might have another eye colour, and hair colour. (unless you're dominant/dominant which means that there are  no recessive genes for other colours).  If you are blond/ blue eyes then you will definately have blond / blue kids.