Madison Ayers is mentioned in chapter 2, "Agenda." He is Zeno Ayers II's oldest brother.
Madison owns a percentage of the Ayers Group Enterprise. As the eldest sibling, Madison represents the senior generation of the Ayers dynasty — part of the family structure that funded Zeno II's early work and helped establish the interstellar ark project.
The Ayers family's collective wealth, spread across stocks, bonds, and debts worldwide — and eventually carried into space — was only possible through the coordinated investment of every family member, Madison included.