Male Southern Residents receive survival benefits from their mothers into adulthood. The Center for Whale Research has demonstrated this "son cost" through their census data, where having a son decreases future reproductive output of a mom. Opus is one example of this. After giving birth to K35 Sonata in 2002 at age 17, she was never documented having another calf.

The K16s (Sonata's matriline) and the K18s (a now extinct matriline) used to occasionally travel separately from the rest of K-Pod. Sonata seemed particularly close with K21 Cappuccino, the last living member of the K18s. Interestingly, since Cappuccino's death in 2021, K-Pod has moved as a more cohesive unit again with it becoming rare for Sonata and his mom to break off.