Structurally related mates, in order of difficulty

[Dann Corbit]

From easy to difficult:

[d]4k2r/1p1b1p1N/1q1p1bp1/2nnb1BN/2PnP3/1QN2Q2/1Q2NRP1/R3KB2 w - - acn 98522; acs 0; bm Ng7+; ce 32756; dm 6; pv Ng7+ Kd8 Qxb6+ Nc7 Ra8+ Bc8 Qxf6+ Bxf6 Qxd6+ Nd7 Bxf6#;
[d]4k2r/1p1b1p1N/1q1p1bp1/2nnb1BN/2PnP3/1QNb1Q2/1Q2NRP1/R3KB2 w - - acn 247940; acs 1; bm N5xf6+ N7xf6+ Ng7+; ce 32756; dm 6; pv N7xf6+ Kd8 Ra8+ Bc8 Qxb6+ Nc7 Nfd5+ Bf6 Qxf6+ Ke8 Qe7#;
[d]4k2r/1p1b1p1N/1q1p1bp1/2nnb1BN/2PpP3/1QNp1Q2/1Q2NRP1/R3KB2 w - - acn 686611; acs 2; bm N5xf6+ N7xf6+ Ng7+; ce 32756; dm 6; pv N7xf6+ Bxf6 Nxf6+ Nxf6 Qxf6 d2+ Qxd2 Nd3+ Qxd3 dxc3 Qxh8#;
[d]4k2r/1p1b1p1N/1q1p1bp1/2nnb1BN/2PpP3/1QNp1Q2/1Q2NRPQ/R3KB2 w - - acn 950486; acs 3; bm N5xf6+ N7xf6+ Ng7+ Qxe5+ Ra8+; ce 32756; dm 6; pv N7xf6+ Kd8 Ra8+ Bc8 Qxb6+ Nc7 Nfd5+ Bf6 Qxf6+ Ke8 Qe7#;
[d]4k2r/1p1b1p1p/1n1p1bp1/3qp1BQ/2P1P3/1NQ2N2/1N2QRP1/R3KB2 w - - acn 260551078; acs 534; bm exd5; ce 32754; dm 7; pv exd5 h6 Nxe5 Bc6 Nxc6+ Be5 Ra8+ Nc8 Rxc8+ Kd7 Rxf7+ Kxc8 Qhg4#;