Can identical twins ever be boy/girl twins?

In some rare cases, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair. 

Can fraternal twins look so similar that they are mistaken for identical?

Yes! Fraternal twins can look remarkably similar!

Can identical twins look different?

Yes! Even though identical twins are from the same sperm and egg and therefore have exactly the same set of chromosomes and therefore genes, researchers are realising that there are other forces at play – the science of epigenetics.

Do you have any resources for twins who have lost their twin?

Yes, please see this link.

Do you have any resources for twins who do not get along with each other?

Yes, please see this link.

Can identical twins ever be boy/girl twins?

Can fraternal twins look so similar that they are mistaken for identical?

What are chromosomes?

Can identical twins look different?

Do you have any resources for twins who have lost their twin?

Do you have any resources for twins who don't get along with each other?

What research is occurring around the world using twins?  Is there a book I can get to give me a "Crash Course in Twin Research"?