My sister passed away, leaving behind her spouse and one child. We were both joint owners of our late parents’ house. Her child has renounced the succession. Can I claim a right of reversion (droit de retour) over her share in this family property?

In principle, yes. The French Civil Code provides that, in the absence of descendants, assets received by a person from their parents by way of donation or inheritance, and still present in kind in their estate, are devolved half to the surviving spouse and half to the siblings (Article 757-3 of the Civil Code). Case law tends to consider that the absence of descendants includes a child who has renounced the succession of their parent (see: Court of cassation, 1st Civil Chamber, 23 May 2012, No. 11-14.104).