The section of your post about first wave of immigration makes sense, and I thought this thread would have more comments trying to put things in historical context like you did.
But I think that led to generations of bi-racial side children more than black white marriages/ couples. The single men would eventually send for their wives and real families.
Why did your white looking cousin stand out ,though? White looking Caribbean folks aren't rare. There's a group of mixed descendants of white slavers and African women in every single country in the West Indies.
Michael Manley, for example.