No problems gali 

J.M: Genetically the twins have black hair however when they became children I changed them to blonde with the 'change appearance' at the mirror.  They look so similar to their twin sisters that I changed the hair colour to tell them apart.  I chose blonde as they have a recessive blonde gene from Skip.  They are indeed first gen sims however the other twins have quite obvious differences.  Thanks for the response.

I'm not sure I understand gali.  What does the ‘Why bother?' refer too?  I'm not trying to get identical twins; I'm merely asking why I managed to get a set of identical twins when allegedly they do not exist.  Most of my twins have slightly different eyebrows, noses or one face is a little longer than another.  Therefore change appearance would not make them identical.  Similar yes, but not identical.

Background:
I resurrected Skip and modified Brandi's controller - pregnancy so she had twins from her pre-programmed pregnancy.  Brandi Broke now has ten children including Dustin and Beau with the remaining 6 children being a further 3 sets of twins.  The last 3 sets of twins were not the result of using hacks or direct modification of the pregnancy token.  The youngest 4 children all have the Aries star sign which I would presume is due to the ‘first born effect' that you mention.  However, here comes the odd part, child 7 and 8 are perfectly identical.

So here's the question J.M., how did I manage to have identical twins if identical twins do not exist within the game?  I have included some pictures for you.

Picture 1
Picture 2
Picture 3

Finally SimPE shows them as having the same eye, hair and skin genetics with only one obvious difference:

5 (dtString) = nose,jaw,ears, for Miranda Broke
5 (dtString) = nose,brow,jaw,ears, for Morgan Broke