Steve was Rudyard Shelton's stepbrother. A comment by Rudyard implies the two did not get along very well.
Rudyard debated naming a newly freed Dragonstorm experiment after Steve, but decided it was "too charming." (Survival of the Fittest)
After the Dragonstorm incident, when Admiral Donald Tennes offered Shelton 4 million in hush money, he requested it be split into four pieces, and a quarter of it go to Steve. He requested it be anonymous as they were "not on the best of terms," so the money was staged as a lottery win. (Disruptive Selection)
In September 2022, Shelton refers to Oscar Shelton as "the only other member of his family" alive, meaning Steve probably had died by this point. (Shelton's Last Day)