1. Section 1(1) of the Intestate Succession Act 81 of 1987 is unconstitutional and invalid to the extent that it confers rights of intestate succession on heterosexual spouses but not on partners in permanent same-sex life partnerships in which the partners have undertaken reciprocal duties of support, as this constitutes unfair discrimination on the listed ground of sexual orientation in violation of sections 9 and 10 of the Constitution. 2. Reading-in is the appropriate remedy where it can be defined with sufficient precision, interferes as little as possible with the legislative scheme, and is faithful to that scheme within constitutional constraints. 3. Under the doctrine of objective constitutional invalidity, pre-existing unconstitutional legislation becomes invalid from the date the Constitution came into force, but a court may limit retrospective effect of a declaration of invalidity under section 172(1)(b)(i) to protect the interests of bona fide third parties and prevent serious administrative disruption, while still providing effective relief to vindicate constitutional rights. 4. In matters involving constitutional validity of legislation, an applicant for intervention must show: (a) a direct and substantial interest in the subject matter; but (b) this is not always sufficient - the court has overriding discretion to grant or refuse intervention in the interests of justice, considering factors such as timing, attitude of other parties, and whether the applicant raises substantially new contentions. 5. "Issues connected with decisions on constitutional matters" under section 167(3)(b) includes ancillary orders that are dependent upon a declaration of constitutional invalidity and were made pursuant to such declaration in the interests of justice and equity. 6. Exceptional circumstances (such as the State's failure to discharge its section 7(2) obligation to amend unconstitutional legislation despite repeated judicial prompting, thereby requiring vulnerable persons to litigate piecemeal to vindicate their rights) may justify ordering the State to pay all parties' costs.