Left: Environment of a CW candidate binary with log₁₀(ℳ_c/M_⊙) = 9.07 and total mass log₁₀(M_BH/M_⊙) = 10.16 at z = 0.032, hosted in a galaxy with log₁₀(M_★/M_⊙) = 12.48 in a halo of mass log₁₀(M_halo/M_⊙) = 14.44. Right: Environment of a CW candidate binary with log₁₀(ℳ_c/M_⊙) = 9.57 and total mass log₁₀(M_BH/M_⊙) = 10.06 at z = 0.42, hosted in a galaxy with log₁₀(M_★/M_⊙) = 12.40 in a halo of mass log₁₀(M_halo/M_⊙) = 14.30. This is one of the highest redshift CW candidates in our analysis, and it is the progenitor of the MBH shown at later redshift in the left panel.