Claim by Foreign Heairs of Son in Grand parents share in self acquired property

2 Acre Farm House jointly Purchased Self Acquired in 1975 Son -B , Son -C ( Expired in2020 ) AND Father AND Mother – for name sack only (in Joint Name) (Both Expired in 1985 and 1995 without a WILL ) OTHER MEMBERS -Son A (Expired ) FOREIGNER and Daughter D Son A (Expired in 2015 ) (much later after expiry of Parents ) UK Citizen with wife and two Children all GERMAN Citizens residing in Germany The property is in possession of SON B and SON C being maintained by spending and paying taxes etc LEGAL QUERRIES 1 Can successors of Son A (BRITISH CITIZEN) i.e Wife and Two Sons (GERMAN CITIZEN) claim the share in Grand Parents Share in joint property ? Neither has come forward for any claim made since the expiry of Grand parents 20 years ago ? 2 Can Foreign Wife of Son A claim the Parents in Law Indian property ? 3 Whether they can have any claim under German Laws