Complex sentence: Membership was once an entitlement of all hereditary peers, other than those in the peerage of Ireland, but under the House of Lords Act 1999, the right to membership was restricted to 92 hereditary peers.
Split into simpler sentences: Membership was once a birthright of all hereditary peers, other than those in the peerage of Ireland. Under the House of Lords Act 1999, the right to membership was restricted to 92 hereditary peers.