Can't neutron stars grow bigger from accretion?
It could steal mass from a companion though that's probably not going to add enough material to matter much. They could merge with a white dwarf or another neutron star if a companion had a slowly decaying orbit. The fact neutron stars larger than 2 solar masses or so are hard to find is probably because this sort of thing is comparatively rare - and if they become too big as result of this they'll collapse into a black hole so like goldilocks it has to be "just right".
Biting the hand that feeds IT
