CLARIFYING ADJECTIVES: OLDER/OLDEST or ELDER/ELDEST?

English for Today by Ganiu Abisoye Bamgbose (Dr GAB)

Both forms are used to compare but while older/oldest can describe things, elder/eldest only describe humans:
This is the elder of the two buildings. ✖️
This is the older of the two buildings. ✔️

Also, elder/eldest is preferable when we discuss age differences in a family:
She is my oldest brother. ✖️
She is my eldest brother. ✔️

Again, older/oldest are used after verbs but elder/eldest cannot be used after verbs:
My sister is elder than my cousin. ✖️
My sister is older than my cousin. ✔️

Finally, junior/senior are not allowed in describing age difference:
She is my junior brother. ✖️
She is my younger brother. ✔️
GAB