I don't care that your kid is dying. edited. ETA again.
He then sends me this message and sob story about how she's sick. I said I couldn't care less about his other offspring and their health. He said she has some sort of cancer, and needs a bone marrow transplant. I asked what the hell he think I'm going to do about it. He then proceeds to tell me that the best match for her is a sibling, and that he needs me to take my son to this clinic and have him tested.
I lost it. Fucking lost it. How fucking dare he not be around for almost seven years and then expect me to put my son through a painful procedure to save a child we have no obligation to and no relationship with.
I told him as such. He said, "you're killing her." I said, "I don't care. It's just a shame it's not you." And blocked him.
The god damned gall of him.
This has nothing to do with him, or our relationship. This has to do with the fact that getting bone marrow is a very painful procedure and I wouldn't put my son through it unless he were dying. I would never ask one sibling to save another. I'd feel the same way if he were an outstanding father. It wouldn't happen.
My concern is my son. Not his kid. I won't out my son through that.
After a comment by another poster, I did a Google search. The transplant won't save her life. At best it will counteract the effects of chemotherapy (which I can only assume she's on, he didn't say). So he wouldn't even be doing anything regarding her life. That makes it especially not worth it to me.