[Trikidiki]

I noticed this a little last year but more so this year.
When I have been hand pollinating peaches I have noticed a number of flowers that had two stigmas. Now the fruit has set there are a few 'fruitlets' that are clearly two peaches emerging from one flower and tightly joined at the base. I tried removing the smaller one of each pair but think that I have probably damaged the remaining one in doing so.

Has anyone experienced this phenomenon or know anywhere it is documented?

[Chrysalis]

Sounds really interesting.  I know nowt about it, but will watch your progress with the twins!
(At first I thought you were referring to your wife/daughter!)
 

[snowdrops]

Isn't it something called fasciation or something similar.

[Trikidiki]

Fasciation is where the stem distorts and looks flat rather than round or like two stems joined together.

I did some digging on the net and it is thought that the twin fruit is caused by drought stress the previous summer.

(At first I thought you were referring to your wife/daughter!)
 

Heaven forbid, with reference to the wife, that is.