A lot has to do with tank size. It's a step away from rams for a moment, but my last group of Pelvicachromis kribensis Moliwe were one pair in a jungle planted 55 gallon with surface fish they chased enough to protect the fry, but no more. Several pairs of those fry reached adulthood in that tank when I wasn't able to catch them all.
You can have a different species in the same set up, and have a radically different scenario. I never had great luck, or honestly, never liked rams so much that I tried many set ups for them. They are among the milder fry defenders, but they can do the job.
I had some South American Pterolebias longipinnis killies in a Moliwe tank once. They spotted the fry and formed a tail to tail 'star' formation that drifted over the fry. 2 would peel off and draw the parents over while the others would dive into the fry and feed. Then they'd go back up, reform the star and the deadly game would recommence. They let each other feed equally and methodically, taking turns as the decoys. These are short lived annual killies, with no time to learn. It had to be behaviour by instinct. It cost me an entire brood of unlucky fry. The parents were African wild caughts, and I did wonder how Peruvian Cichlid parents would have reacted. Maybe they have counter moves.