Something strange I have observed is that some unique life events or patterns run in some families, such as being a single parent, experiencing (non-genetic) issues in conceiving a baby, losing a loved one, and facing a similar accident in life. While such reoccurrences within families need not necessarily dictate ancestral karma, the mere fact that an undesirable life event manifesting in more than one or two members related through blood does give rise to a possibility of a transgenerational inheritance.