Can I pursue my crush if he is already somewhat affiliated to my friend?

I have a crush on my brother's friend, let's call him A. My brother and I have a mutual friend, let's call her B.

B broke up with her partner recently and my brother had the idea to introduce A to B. So the narrative that was set at that point in time, is that there is now a bridge drawn between them.

The four of us became mutual friends recently after meeting at a common setting and both B and I got to meet A face to face and know him better through this setting. (I never got to know A better or spend time with him previously because we only knew of each other's existence but never had the opportunity to get to know each other.)

I still have a crush on A but no one knows anything because I never spoke up. I also treasure my friendship with B. But am I not allowed to speak out now or pursue my crush because the ship has sailed? Is there some kind of unspoken 'Friend Code' thing where I have to stop now and just let my crush die out internally and move on? Is it maybe rude to B if I do pursue my crush, even after knowing that she was introduced to him first? I don't know what to do... any advice?
Can I pursue my crush if he is already somewhat affiliated to my friend?
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