Complex sentence: It was there that he met Nestori Miikkulainen, four years his senior and who later featured in Vainio's song "Vanhojapoikia viiksekkäitä" ("Moustached Bachelors").
Split into simpler sentences: It was there that he met Nestori Miikkulainen, who was four years older than him. He later used Miikkulainen's name in the song "Vanhojapoikia viiksekkäitä" ("Moustached Bachelors").