I love Requiem, but I think that other threads here have dealt extensively with how such pairings may be made and what sort of criteria to look for when making such pairings.

I think you’d be better off using Requiem with Whitney because they’re by the same designer. Those Requiem ligatures are such a cool concept but I wish there were more of them, like ‘gg’ or ‘ir’ would be tops.

The only problem with the “same designer” logic is that it’s only a starting point. When you actually compare Whitney and Kievit, you see that Whitney is much coarser, with Grotesque features that aren’t nearly as sympathetic to Requiem. Depending on your usage, Kievit should pair quite well with Requiem.

Use fonts by the same designer when that designer tends to make a lot of type that’s similar (Zapf, Unger, Gill); but with eclectic designers like Hoefler, Schwartz and Carter, it’s not as safe a policy.