also my grandmother was infected at birth because her siblings are also hep b carriers. we found this out recently as they were also tested.
Not all sibling are infected. My grandmother was a carrier and my mother and her 3 brothers are also infected at birth, but oldest sister / sibling had antibodies. We do not know when my aunt / moms oldest sister developed antibodies but it was before she gave birth because her children are also hbsag - . From what we think maybe my grandmother was a inactive carrier while pregnant with my aunt and gave birth to her and became active after giving birth. The 3 children after are all carriers but she was not, but she does have hbsab.
Hopefully studyforhope or Stephen can respond to that one. I tried looking but cannot find if HbeAb would stay positive forever, or has the possibility to go negative with resolved case. I do believe HbcAb stays positive for life or a very long time, like your mom. It's amazing how complicated HBV is.
I'm wondering if your mom was infected and transmitted the virus to you and your brother, but was not infected when your sister was born, unless she is the middle child. In that case, she could have cleared the virus. Has she tested the core? Also, if your mom was infected with all 3 of you, maybe she was just lucky and didn't get it. Or, you or your brother got it from her and the infected one of you passed it along to the other brother via a cut, open wound, etc.
At any rate, since your mom has that positive HbcAb means resolved infection, not from vaccine.m So, my guess would be that it stemed from her and your sister was lucky.
assuming that hbcab + can not pass the virus, your mothers window of being infectious is 6 months, give or take.
There are some scenarios which could have occurred for you:
1.) Your mother was infected at the time of your birth, her body cleared it in due time, developed slight anti-bodies and it was made better with the vaccine.
2.) You and your brother could have both been infected within the first 5 years of your life. Maybe it was through blood transfusions or anything else at the hospital right after birth (or something within the first 5 years for both of you). After all, there wasn't this type of monitoring 39 years ago.