Aisha’s exact birthday is unknown, but she was born *before* 610 CE when Islam was revealed.
Aisha is recorded as accepting Islam shortly after it was revealed. She could not have done so as an infant or toddler. The youngest she could have accepted Islam would be 7 y/o, but that’s a guess.
She was married in 622 CE 12 years after she accepted Islam. (7 + 12 =19 years).
Further, Aisha fought in the Battles of Badr and Uhud (624/5 respectively). No one *under* 15 fought in those battles, let alone be a leader of them.
Also, Asma, Aisha’s eldest sister (by ten years) died at age 100, 72 years after Aisha’s marriage.
Process of elimination and mathematics, Aisha could not have been married before she was 14 and the consummation before she was almost 20.
By mathematical reasoning:
622 + 72 = 694 -100= 594 year of Asma’s birth.
622-594= 28 yr of Asma at Aisha’s wedding
Asma is recorded as ten years older than Aisha. Therefore:
28-10= 18 Aisha’s age at wedding.