are intestate succession hiers are joint tenants

my step mother died,she owned a plot,leaving 3 legal hiers, husband,son and daughter.what kind of property ownership is it is it joint ownership as land is still registered in deceased name,if my father dies will the plot devolve only to her son and daughter as is in the case of joint tenancy.or me(2 nd wife's only son) will get share being hiers of her husband.can my father will his 1/3share to me, because I have read that joint tenancy doesn't allow will execution.please explain if the 3 legal hiers are joint tenants of the plot or intestate succession hiers.