en.wikipedia.org/wiki/Cardinal-nephew

The article itself defines a cardinal-nephew broadly as "a cardinal elevated by a pope who was that cardinal's relative." Under that definition, 1689 cannot be the last such appointment.

Credible reference works document later examples:

• Treccani's biography of Pius VI states that among his many cardinal appointments were those of "the nephew Romualdo Braschi-Onesti", and Treccani's standalone biography of Romualdo says that "Il 18 dic. 1786 ebbe la porpora" (he received the red hat on 18 December 1786).
• A Vatican publication on the Pontifical Academy of St. Thomas says Leo XIII "named his brother Giuseppe ... as cardinals" in 1879 and later explicitly identifies "Cardinal Giuseppe Pecci, the brother of Leo XIII."

So while 1689 may refer to the last holder of the curial office of Cardinal Nephew under the old system, it is not the date of the last cardinal-nephew in the broader sense used in the article's opening definition.

Standard biographical references give Pius VI's nephew's name as Romualdo Braschi-Onesti.

Treccani's dedicated biography is titled "BRASCHI ONESTI, Romualdo" and identifies him as the son of Giulia Braschi and the nephew of Pope Pius VI. Treccani's biography of Pius VI also refers to the same nephew as "Romualdo Braschi-Onesti."

So this occurrence of "Romoaldo Braschi-Onesti" is an incorrect spelling of the cardinal's name.

This overstates what Romanum decet pontificem did.

Innocent XII's 1692 bull curtailed nepotism and limited future popes to creating no more than one cardinal-relative; it did not end the broader practice of promoting papal relatives to the cardinalate. Later, Pius VI elevated his nephew Romualdo Braschi-Onesti in 1786, and Leo XIII elevated his brother Giuseppe Pecci in 1879.

So 1692 marks the abolition of the office of Cardinal Nephew and a major reform of papal nepotism, but not the complete abolition of the practice of elevating papal relatives as cardinals.