A siren's pod is a complex social group, where females go out to sing for negative energy and take care of the pups and juveniles and the males are more often than not too busy maintaining a perimeter to keep monsters and predators away. Of course parents are allowed a day every so often to spend time with their pups if they have one, but there are times when both males and females are each obligated to their tasks given by the Matriarch and the vulnerable young need to be cared for.
The answer most pods have come up with is the "Auntie System", where one siren remains behind instead of singing to some village, port, or cruise vessel. Matriarch often assign mothers who've lost their pups to circumstances as they often 'adopt' the squirming little ones as their own for a short time. Ensuring they are well looked after as if they were her own and ensuring mental sanity for the mourning mother. The Auntie will teach hatchling sirens to sing and entertain the siron young in the process, switching over to hunting techniques for both genders to learn and oversee play fighting between brothers and sisters of the pack. If she ever feels threatened, she has little to chose from as she cannot fight or run least she risk the future of the pod and the wrath of the parents and the Matriarch.
Instead, she'll use her body to shield and cover the younglings enduring any damage necessary while using a unique and rarely voiced vocalization that calls every male within ten miles. The call has an agitating effect that sends sirons into a defensive frenzy and will drive off most offenders once they arrive to the site. An Auntie might try to move the pack 'clutch' to dense cover for protection, but they generally lock into place and at best might try to burrow into the sand to offer the pups better cover where her own bulk serves as the 'door'.
Usually the call is rarely used except when a Hammerhead Moray or an Oceanic Dragon attacks, and upon the return of the females and the Matriarch the parting gift the hatchlings give are nuzzles, licks, and show of gratitude which cements a good bond with each Auntie.