In the twin, the colour of a piece is changed, and the same moves are then made by a piece of the same type of the opposite colour.
Abdurahmanović, Fadil
Kalkavouras, Ioannis
Problem Paradise, 2015
1st Prize
a) 1.Rc4
Bd8+
2.Kc5
Bc7
3.Be1
Bb8
4.Bb4
Ba7#
b) 1.Bd8
Ke8
2.Bc7
Kd7
3.Bb8
Kc8
4.Ba7
Bd8#
Shorokhov, Boris
10th FIDE World Cup, 2022
4th Prize
a) 1.Ra8
Sxe6
2.Rh8
Sxd4
3.Rh1
Sb5
4.Ra1
Sc3#
b) 1.Sxf8
Ra8
2.Se6
Rh8
3.Qb4
Rh1
4.Ka3
Ra1#
FEN: 5N2/r1pb1p2/Pbp1nPp1/p1p5/P2p4/qp6/kn2K3/8
External links:
Semenenko, Valery
U.Degener-64 & M.Degenkolbe-60 JT, 2024
3rd Prize
a) 1.Bc8
Kxg2
2.Bd7
Kf1
3.Be8
Ke2
4.Bg6
Ke3
5.Be4
dxe4#
b) 1.c3
Bc8
2.c2
Bd7
3.c1=S
Be8
4.Sb3
Bg6
5.Sd4
Be4#