Miles (this spelling) is a wonderful name. Why not pick something with a similar simplicity and history to go with it? Replacing the letter i with y is a dated trend that has already run its course, and McNames were right behind.
I would probably avoid M names unless there’s something that really speaks to you, to avoid making them sound too matchy. They’re human beings, after all, not a tea set. What about
Miles and
AliceMiles and
CecilyMiles and
ClaireMiles and
EvelynMiles and
HazelMiles and
HopeMiles and
JaneMiles and
JuneMiles and
LydiaMiles and
PearlMiles and
RosemaryMiles and
Sylvie