A DBB-bonded unit's Bonded Brave Burst and Bonded Super Brave Burst are the Brave Burst and Super Brave Burst of the DBB-bonded unit's partner.
E.g. Xenon's BBB/BSBB would be Estia's BB/SBB.
IMPORTANT NOTE: SP Enhancements of the DBB-bonded unit's partner are NOT counted towards the BBB/BSBB. (so Xenon's SP Enhancements do not count towards his use of Estia's BB/SBB, and vice versa)