On pairs of definable orthogonal families

We introduce the notion of an M-family of infinite subsets of $\text{nn}$ which is implicitly contained in the work of A. R. D. Mathias. We study the structure of a pair of orthogonal hereditary families $\text{aaa}$ and $\text{bbb}$, where $\text{aaa}$ is analytic and $\text{bbb}$ is $C$-measurable and an M-family.