99 as 2 halved is 1 so 100-1= 99
When you were 2, your brother were 2/2=1. So you are one year older than your brother. If you are 100 now, then your brother is 100-1=99.
Dalam Islam, iri hati (حساد, hasad) dan dengki (حسد, ḥasad) dianggap sebagai sifat tercela dan termasuk dosa.