I think
Linden and
Alasdair would make an awesome brother set!
Linden is a fine first name for a boy, but it also works as a middle name.
Alasdair is my favorite spelling. It's one of my top favorite names for a boy. I don't think it would be in poor taste to reuse it if you really like the name.
I pronounce it two ways. It depends on my mood. The "proper" pronunciation is the way you say it...AL-eh-stir. However, when I'm feeling extravagant I like to pronounce it al-ehs-DARE.