The "feel" of Amelia is sort of 20s/30s for me. If you google "parents connect baby names world" you should get to a page where you can check meanings, when it was popular, etc... I'm looking at it now, and aside from a bit of a dip in the 60s and 70s, it's been fairly steadily popular I absolutely love the name Amelia, if Cookie's a girl that'll be her name

As for sibling names that go with it... Thomas jumped out at me immediately. Julia, Adele...