No, he has two older sisters, Whitney and Hilary.
Michael is older than Whitney.
The reason Michael Phelps actually became a swimmer because his older sisters Hilary and Whitney were swimming all the time and so naturally Phelps followed the family tradition and it turned out he was better than either of his older sisters. It was not because he had a perfect body alignment because 9/10 the most successful swimmers in the world are not built for swimming, but he succeeded in swimming because he had the most determination and probably the best coach in the world Bob Bowman.
YES
Yes, by approximately eleven months.
I think Hilary is older. Andrew looks the youngest.
His oldest sister Whitney was born in 1978 and Hilary was born in 1980. So currently they are around 34 and 32.
Whitney had a biological brother named Michael Houston who is a year older than her. She also has an older brother named Gary from her mother's previous marriage, and an older brother John III from her dad's first marriage. And she has a step-sister Alana as well: after Whitney's parents got divorced, John re-married and had a daughter.
Haylie Duff is 3 years older than Hilary, who is 23.
Halie Duff is older
Hilary Duff doesn't have any brothers, but she has an older sister.
Whitney Houston was born on August 9, 1963 and died on February 11, 2012. Whitney Houston was 48 years old at the time of death.