
Are you in any way hoping to date them? That could cause nerves. Could also be afraid you’ll get in trouble or get made fun of for how you behave around them, or that you’ve been taught to put men and women in separate categories in your mind and therefore automatically assume interactions will be different/new/scary.
And for the inability to say something, you can pick something you know you can talk about and then plan what you’ll say ahead of time. Maybe rehearse in the mirror. Then go say it. Once you start talking, that might override your brain’s freeze mode. It might not, but that’s an idea.