Hereditary causes of sinus bradycardia? mine is the most severe requiring a pacemaker, but mother and uncle (not fit) also have bradycardia. any link?

Yes , could be.: Asymptomatic sinus bradycardia is often a sign of good physical conditioning. However, it can be pathologic, symptomatic, and potentially life-threatening. Unexplained sinus bradycardia is associated with a mutation in the gene (HCN) that encodes the pacemaker channel, the channel responsible for sinus-node activity. They may need genetic testing.