I'd like to know how something can be "related" to another biologically without in some way "descending" from it. Also, I thought "common descent" was an evolutionary principle, with all life eventually traceable to the lower, smaller, or simpler life forms. Not that there is a single evolution story. Which one do you believe?
A brother is related to his sister but he did not descend from her.
Many people are related to their cousins, but not descended from them. Further back in time there was a common ancestor to be "descended" from, but two creatures can be related without one being descended from the other.
I am closely related to my sister. She is not my mother. My niece and nephew are related to me, but they are not my children. This isn't very complicated stuff.
Are you related to your niece? I am (my niece, not yours). I am clearly not in any fashion descended from my niece. We do, however, share a common ancestor.
"I'd like to know how something can be "related" to another biologically without in some way "descending" from it."
Well, for example, your cousin isn't your mother, unless you're from West Virginia.
Are you related to your sister or brother?