Hm, I pronounce Alicia "Alissia".
Romilly is nice and unusual.
Know what you mean about Ione - it makes our last name sound like a noun too.
Don't know about the cousins thing. In my family heaps of boys are named some variation on James, but not first names and first cousins. If you are close to your brother and talk to him lots if might be a bit ... I don't know, confusing, maybe? By the same token if you were absolutely set on Astrid maybe you should use it regardless. Sorry, not helpful, I know. My SIL - who lives thousands of miles away- is due a few weeks after me (both having girls) and I am going to try every trick in the book (bar an elective at 39 weeks!) to make sure mine comes out first so I get first pick of the names!
Have you tried calling your DD different names and seeing if any of them feel right?