Complex sentence: On 29 February 2012, Opel announced the creation of a major alliance with PSA Peugeot Citroen resulting in GM taking a 7% share of PSA, becoming PSA's second-largest shareholder after the Peugeot family.
Split into simpler sentences: On 29 February 2012, Opel announced the creation of a major alliance with PSA Peugeot Citroen. At that point, GM became PSA's second-largest shareholder after the Peugeot family.