Each solution begins with a move up one square. More importantly, the twins have the switchback of the promoted P to f7, the different pure round trips over three moves with the intervening white g-pawn, (a) Qf7-g6-e8-(wPg6+)-f7 and (b) Qe8-h5-(wPg6)-e2-e8, the switchback (a)&(b) bKh7-h8-h7, the pure round trip (a)&(b) bKh7-h8-g8-h7 and finally the various switchbacks, (a) bKh6-h5-h6 and (b) bKg8-f8-g8. They are therefore a good twin pair. Kindergarten problem.