Having parents or siblings with BP (or just BPD) can make life easier, because at least there is someone who (maybe partly in case of just BPD) understands, but also a lot harder! It's like a double-edged sword in my experience. I don't know which side cuts deeper.

In some way, BP might not be just propagated by genes or epigenetic means, but also by family dynamics. However, parents or siblings with untreated mild BP symptoms may have a more detrimental effect than those are being treated for BP. A parent may also be in denial and deny the possibility that his or her children could be affected. The BP characteristic of projecting one's own difficulties and wishes onto others might counterbalance that to the extent that a child may receive the necessary care sooner, in untreated (and treated) parents.

Family dynamics may be less of a problem, in this way, with schizophrenia, though I wouldn't wish that on anyone. Results of family history/incidence studies might point in that direction. But that is largely guessing.

That BP traits are "transactional" in parenting is pretty likely.

Anyways, you are not alone. Try to explain your behaviour as openly as possible. If you get agitated in trying, realise that you probably haven't found the right approach or words. Of course, maybe your parents are very understanding and all. In that case, please don't mind my completely superfluous advice.