They say, (I mean English speaking peaple) older, elder and all that stuff. Frankly speaking, I am in a mess. I need your help, my dear friends.
Thanks a lot, Igor from Ukraine.
I hope Harry won't mind my elaborating on it a little.
elder, eldest is only said about members of the same family.
the elder/eldest child/son/daughter
Brian is the eldest child in the family.
Brian is two years older than his sister.
BTW sometimes people say eldest and not elder when they only have two children.
Rosalie, our eldest, is dead set to become an actress.
If you want to be polite, you say
She's an elderly lady, not She's an old woman.
Of course I don't mind. I just wanted to tell him the difference between "older" and "elder". The topic is large, even much larger than you introduced.