No, bristlenose plecos usually don’t eat their babies. Unlike most other fish, bristlenose plecos typically don’t try to eat their own eggs or young. Some first-time parents might try to eat several of their babies, especially if they lack food, but they won’t completely decimate their fry.
However, just to be sure, you should install an in-tank fry saver or fry trap, especially if the fry are starting to leave the cave where they first hatched. Doing this will keep them safe until they’re at least four weeks old or until they’re big enough to fend for themselves.