It would depend on the specific circumstances, of course, but I think in those age ranges and as you describe it here it would probably not be considered abuse per se - more like childhood experimentation.
That said, even with the same age range, add 3-5 years to both children and I think it would be much more likely to be viewed as abusive.
Re: "It doesn't lessen you as a person in any way."
Similarly, self-compassion is a way to avoid the trance of unworthiness:
Effects of Childhood Sexual Abuse
Child sexual abuse (CSA) has lifelong effects. Adults who are survivors of CSA often report a feeling of being ?stuck?. Their efforts to build and manage their lives often seem fruitless, hollow, or even hopeless. There can be a persistent perception that they are somehow different from others. They commonly report feeling that they are on the outside looking in or believe that they just don?t belong.
Often, these symptoms are a mystery to...
Charlottetown survivor of childhood sexual abuse leads awareness group
WARNING: This story contains discussion about child sexual abuse and may be disturbing to some
By Laura Meader
May 13, 2016
A survivor of childhood sexual abuse says there needs to be more awareness about the problem and less fear discussing it.
Kate Eastman of Charlottetown has set up an organization and a special walk to bring the issue into the spotlight.
Eastman was sexually abused by her stepfather starting when...
Wish the very best for you and your family Sarah. So sorry for what everyone went through.
As you go forward keep in mind your family members need to take some responsibility also for whatever help they may want or need - remember that you can't do everything for everyone. Not sure whether seeking some sort of family therapy as a unit is what you have in mind, or whether members prefer to seek help individually. One option I guess would be looking near you for a psychologist, therapist, or...