I think you should see a second opinion.
There seems to be a type of BBB that is genetic -
BBB are common, though, so it could be coincidence.
In itself, an LBBB can be harmless. If you are having symptoms, it can be part of a bigger problem. https://www.mayoclinic.org/diseases-conditions/bundle-branch-block/symptoms-causes/syc-20370514
I would ask for a referral to a cardiologist, if for no other reason than an evaluation given your symptoms and what your mom and sister have gone through.
If a cardiologist hasn't ever evaluated your elevated heart rate and palpitations, which could be nothing serious at all, or could indicate something else, then you should see one.