So if Zeke is Eren's brother, that's why Eren has the power to control the Titans like Zeke
No honey, it has nothing to do with broterhood of eren x zeke
Eren power to command titan comes from reiss-titan that grisha eaten. The progenitor titan.
What in question is zeke's power.
Why he could command titan,, so zeke's function not that much different than progenitor titan,,, or maybe progenitor titan has another capability,,,, (beside the legacy of first king)
Maybe like activated titan in the wall, maybe
http://www.mangago.zone/read-manga/chuan_yue_xi_yuan_3000_hou/mf/e76eecd292f3a58b/Ch7/pg-2/