Older vs Elder
Elder, eldest used for seniority within a family
Yet the elder Bush turned out to have had the better foreign policy.
Being the eldest child is a blessing and a curse.
Science again says the eldest child Is the smartest of all the siblings.
Eldest, oldest and youngest are used of only two people
His eldest boy is at school; the other is still at home.
Meanwhile, my son will be sent to live with my eldest sister.
NOTE! Elder is not used with than
He is older than I am.
She is 3 years older than me.