Kelsey turned 25 in 1999 so she was born in 1999-25 = <<1974=1974>>1974
Kelsey's sister is older by 3 years so she was born in 1974-3 = <<1974-3=1971>>1971
It's currently 2021 and Kelsey's sister was born in 1971 so she is 2021-1971 = <<2021-1971=50>>50 years old
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