general dx question?

[nats]

we have a family member (no details for the sake of anonymity) who frustrates us a lot e.g. s/he does very mean and hateful things and when confronted seems completely unaware/dismissive and strongly defends their innocence. we weren't raised together but we're increasingly wondering whether a borderline and/or dissociative (tho probably not DID) dx would explain all these behaviours. since we're not a T, we'd value anyone's thoughts/experiences of borderline diagnoses alone or combined with a dissociative dx. thanks!