Hi Maud, my partner is in a similar situation.
She had a 3 way Joint Tenancy with her parents and survived over her mother then recently, her father. The 3 off them lived in the property. Both my partner and father have contributed to the maintenance, improvements, landscaping and furnishing of the property and gardens. He died intestate. The property passed to her under survivorship. NOW her siblings as administrators of his estate claim that garden shed, greenhouse, fish in pond, pond pump, trees, shrubs etc, carpets, rugs, crockery items etc etc in fact anything paid for by her father, whether, fitted, fixed or movable....is an asset of his.
Are they right? My partner does not claim ownership of any personal effect of her father (or mother).