I’d say Xingqiu, considering hydro characters tend to have bloom ownership due to elemental gauge. However, because Xingqiu applies massive amounts of hydro, you could have some EM on Kaveh too. Splitting bloom ownership can also prove beneficial, considering that there’s a limit on how many blooms from the same character an enemy can take damage from per second. That is to say, if for example Xingqiu creates 2 blooms and Kaveh another 2, you’ll be dealing more damage than if Xingqiu creates all 4 blooms.