First of all he was not a “kid”- he was 14-15 years old at the time this took place. But his sisters were younger - 12, 10, 8 and 4 years old.
Next, I don’t know what kind of world you live in, but there is a very big difference between a boy or teenager out on a date with a girl (hopefully not his sister) and perhaps doing something like putting his arm around his date and sort of accidently on purpose brushing her breast (i.e. copping a feel) and an older brother sneaking into the bedrooms of his own sisters on multiple occasions and fondling their genitals – not just their breasts but their “nether regions”, including that of his 4 year old sister while they are sleeping.
The former is normal teenage boy behavior; the latter would be molestation bordering on incest.
Since when is 14 NOT a kid?