The Si1132, Si1141, Si1142, Si1143, Si1145, Si1146, and Si1147 have a command that allows you to change the i2c address of the device
how do you use that? I see no reason to change the save addres other than having two devces, otherwise with the same address. Thus such a command wuld go to two devces
If you have a way to control the VDD of the Si114x, either by powering it from a GPIO or controlling a mosfet on its power, you can power one up and change its address, and then power the next one up to avoid any conflicts.