Why no one recognize white slaves?

Hi. I am new here, but all the time I hear about slavery, I hear only about black people (Africans), but slavery is much bigger topic, and it contains a lot of other slaves then just slaves from Africa. I am from Ukraine and know about slavery that happened with people of Ukraine and Russia. Whenever one people (aristocrats) used to abuse and enslave so-called "low-born" people. Those aristocrats murdered people, sell them to each other, punish and did everything that have been done to black people and even more, but no one talks about it. Everyone focuses only on black people. Why? I feel upset that my ancestors not being recognized. My ancestors fought for their freedom and here are a few examples. Do you know about "Cossacks"? Cossacks were slaves that escaped their owners and started to live on their own. Those people become power of their time, but they were slaves that escaped from their owners. Do you know about Taras Shevchenko? He was strong poet and author, and he was slave. His poetry encourages people to fight for freedom. Thats all, but please respond to it. I am really concerned that no one knows about struggle of my ancestors. Thank you for your attention and have a great day.