Introduction: Unilateral lambdoidal craniosynostosis is a rare disorder that occurs in approximately 3 % of all craniosynostosis phenotypes and only 0.03 % of one million live births. It is even more unusual for this type of synostosis to occur in siblings with only two other cases reported in the literature. Case report: We report a set of full-term dizygotic twins born with lambdoidal synostosis and a family history of connective tissue and cardiovascular anomalies. One of the twins also had concomitant bicoronal craniosynostosis. Conclusion: True familial lambdoidal synostosis is exceedingly rare. The present cases in dizygotic twins occurred in a family with a significant history of connective tissue disease suggesting a possible association. © 2013 Springer-Verlag.