We identified 13 clinically relevant germline variants in known cancer predisposition genes including TP53, ETV6, MSH6, MLH1, and BRCA1. Notably, we uncovered novel candidate variants in ATR, TNFRSF9, ETAA1, and KSR1, which was supported by segregation analysis, consanguinity patterns, and secondary malignancy phenotypes. Here, TNFRSF9 is linked to cancer.