While Lucy and Milo share the soft sounds and imageries and Lucy flows especially well with V-C, I actually see Pearl as a better match to Milo - both vintage-cute names. Milo & Pearl would go work siblings like Felix, Jasper & Olive.
Lucy, to me, goes more with names like Edmund, Arthur, Peter, Simon & Charles etc (ie more
“classic” English names) and therefore maybe Miles. But Milo feels more in top category.