I watched it from a sense of macabre fascination I'm afraid, because 20 years ago I worked in the same office as Karen & Karol Groom (yes, back then, they even worked together).
I never really knew them (in different depts) but was aware that some of the younger lads (late teens, early 20s) really used to take the p* out of them .... not for being twins per se, but for being a bit "odd". I swear that what they wore back then at the age of 19 was the same as they were seen wearing in the show - not very flattering at any age.
They certainly came across - despite being smiley and polite - as very insular, and very innocent .... which led to the teasing. How much they were aware of it I don't know ..... quite possibly their innocence actually protected them from understanding the gist of it. It was quite obvious they had no interest in the opposite sex and were the opposite of all us other fashion-conscious teenage girls who worked there.
I suppose if they are happy who are we to criticise the way they choose to live, or dress. But I think the lack of experimentation - with clothes, and with relationships with other people, is definitely a side-effect of having all your emotional needs provided to such a complete extent by another person. Is that necessarily wrong, or does it just seem that way to the vast majority who aren't identical twins and who can't imagine life so closely bound with another.