simplelogin for sms is definitely a space lacking in the consumer product market.

family home management and communication routing in general is a blank space with almost nothing. it extends into every market. childrens medical bills only appearing in one of two parents accounts etc. communication from an entity to a family is ripe for disruption and standardization.

have you looked at business support tools such as https://missiveapp.com/blog/what-is-sms-shared-inbox