Which Pair of Siblings Is Likely to Be Past the Peak

Which pair of siblings is likely to be past the peak period of sibling rivalry?

A) Adam,who is 8,and Glenn who is 6
B) Beatriz,who is 13,and Alma,who is 15
C) Akbar,who is 4,and Khalid,who is 5
D) Donte,who is 9,and Traylor,who is 11