  The investigation of twist engineering in easy-axis magnetic systems has
revealed the remarkable potential for generating topological spin textures,
such as magnetic skyrmions. Here, by implementing twist engineering in
easy-plane magnets, we introduce a novel approach to achieve fractional
topological spin textures such as merons. Through atomistic spin simulations on
twisted bilayer magnets, we demonstrate the formation of a stable double meron
pair in two magnetic layers, which we refer to as the "Meron Quartet" (MQ).
Unlike merons in a single pair, which is unstable against pair annihilation,
the merons within the MQ exhibit exceptional stability against pair
annihilation due to the protective localization mechanism induced by the twist
that prevents the collision of the meron cores. Furthermore, we showcase that
the stability of the MQ can be enhanced by adjusting the twist angle, resulting
in increased resistance to external perturbations such as external magnetic
fields. Our findings highlight the twisted magnet as a promising platform for
investigating the intriguing properties of merons, enabling their realization
as stable magnetic quasiparticles in van der Waals magnets.
