I love Celtic names, but so many of them are hard to pronounce. The spelling looks like one thing, the pronunciation sounds completely different...

I prefer Darken and Richard as brothers. As you say, it's a richer and less often explored relationship. I feel like stories and popular media often focus on parent-child or romantic partners relationships, rather than friends or siblings. My theory is that those (parent-child, lovers) are either simpler, or else people think they are.

That's one reason I love that Richard has so many Sibling Issues ;)