are Rin and Len brother and sister o what

No, they are considered "Mirror Images", hence the "Kagami" in their last name with means "Mirror". I guess the publishers of Vocaloid changed them to "Mirror images" with all the Twincest out there. xD

They`re Mirror immagini of themselves , but te can say they`re twins . cause twin = 2 . and yeah . fan think of them as twins.

KEI stated in an interview that he specifically did not design them as twins, and was told the two are più like mirror immagini of eachother and design them as such da CFM. He detto since he didnt design them at the same time (Rin came first), Len ended up looking a lot like Rin and was mistaken as her twin brother. He did not mean for them to be twins.

EDIT:
Len's voice is not altered in any way. Asami Shimoda was hired because she is able to create both male and female sounding voices. Len is Asami's raw voice without any editing :]

She sings as both Rin and Len in Rin Rin Signal ( link )

there's really no official explanations. some people prefer calling the two of them "mirror immagini of each other"--but since they're not exactly "identically mirrored images", they can be considered twins (brother and sister) as well.

i doubt thaey are caues they make so many Amore songs togather

Well, Rin and Len can be brother and sister. Also they can be a couple. See, the people who created them did not give us an obvious answer. But, they let the fan choose if they are brother and sister o a couple. Personally i think of them as a couple because of all the Amore songs they created. Ex. magnet,spice ext... But te can also think of them as a couple da the songs, Servant of evil, daughter of evil ext... it's up to you. :)

No they are not! Crypton made them as "mirrored images". They did not officially say if they were twins, innamorati o siblings. They left it the way it was so as not to ruin everyones creativity. It is the fan's decision to pick what they are.

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Rin x Len 4ever

Yes they are because the same last name and they are twins

Len and Rin are actually mirror immagini as everyone are saying. Also the creators of VOCALOID (crypton) decided to leave rin and len up to the users to decide what they could be in there video . they could be lovers,twins,ect. The last name "kagami" does mean "twin"... just cerca it up,it will come. X3

Actually, I've heard that the creators of them detto they were originally mirror immagini of eachother, but fan can interpret them as whatever they want. (twins, lovers, etc.)

Len is actually the mirror image of Rin so,or what.

They were originally mirror images. But then they were boyfriend and girlfriend, and then twins. It's okay to refer to them as brother and sister, since they are, but they are also the other things I listed. It's confusing...

No,they are mirror images.

It depends on the song they are Canto
Example:
In their song adolescence they are lovers

As te people can see.. about 70% Rin Len songs has them as lovers, 20% as twins and 10% as mirror images.. but this doesn't make them any in particular.. Mirror immagini is the main concept.. while fan can think of them in anyway they want...

They are TWINS DON'T TELL ME THERE F***ING MIRROR IMAGES!!!-
And there not lover's eaither sorry to burst you're bubble... of course I have always thought of Ishiko and Len to be a couple... Idk why....

well in my opion there innamorati they may seem like twin but to me there just plain innamorati they sing a lot of Amore songs and they seem like the perfect match that's my opion anyone can deal wth that -_-
Sugarcube OUT

Yes crypton intended them to be twins but they are actually mirror immagini hence their last name Kagamine. Kagami meaning mirror and ne being sound. The reason I think is to give the fan that choice but also the fact that in some songs they're innamorati and it'd be awkward if they're siblings.

yes!!!

brother and sister they are not lover they are twin te can see da there eye color.

They can twins. o lovers.
innamorati song: Cantarella
Twins song: Electric Angel