Diego Romo de Vibar con Mariana de Villalobos

I am trying to figure out a relationship: the above-named couple certainly married, as proved by the baptismal records of three of their children (Beatríz, 1712, Teocaltiche; Sebastián, 1717, San Juan de los Lagos; and Monica Gertrudis, 1729, Jalostotitlán—and, yes, they seemed to move around a bit) and the marriages of two others (Ana Juliana m. Juan Joseph Pantaleon de Aceves in 1745 in Jalos; and María Margarita m. Xptovál Joseph Gomes Cornejo in 1741, also in Jalos). In each of these records—whether baptisms or marriages—the names of the parents are explicitly stated.

There is also a marriage record dated 14 January 1686 in Teocaltiche of Nicolás Romo de Vibar and Mariana de Villalobos. The parents of Nicolás are given as Diego Romo de Vibar and Luisa de los Anjeles, who I presume is María Luisa de los Ángeles Villalobos Castillo de Sandi; and the names of the parents of Mariana are given as Nicolás de Villalobos (ya defunto) and Teresa Carrillo.

My questions, then, are these: (1) how are the two women, both named Mariana de Villalobos, related, if at all; and (2) where does Diego Romo de Vibar fit into that family—in other words, are Diego and Nicolás related? I might be tempted to think that the two Marianas are the same person, except that a marriage in 1686 would mean that she would have had to have given birth to a child in 1729 in the 43rd year following her first marriage—an unlikely occurrence.

The line I am following is that of Diego and Mariana, named in the subject line. Any documented light that can be shed on these questions will be gratefully appreciated.

Sinceremente,
Lawrence Bouett