older adult
A person past middle age, perhaps (but not necessarily) elderly. Now that I'm an older adult, I have all these aches and pains that I never felt before. You don't have to speak loudly to them, you know—not all older adults have trouble hearing.
older brother
A male who is older than one or more of his siblings. I'll ask my older brother to help us with the move. Connie's older brother will be there on Saturday, and I'd really like you to meet him. Our neighbor Jim was like an older brother to me when I was growing up.
older sister
A female who is older than one or more of her siblings. I'll ask my older sister to help us with the move. Connie's older sister will be there on Saturday, and I'd really like you to meet her. Our neighbor Jill was like an older sister to me when I was growing up.