Photonic chips with silicon nitride (Si₃N₄) microring resonators are well established as heralded single-photon sources, but their operation as frequency-degenerate twin-photon sources has not previously been demonstrated. Here, we realise a twin-photon source at telecommunication wavelengths in a Si₃N₄ ring microresonator via an inverse four-wave mixing (FWM) process, in which two photons from spectrally distinct pumps are converted into a pair of identical twin photons. The measurements show a maximum coincidence-to-accidental ratio (CAR) of 5.4±0.6. In addition, the microresonator functions as a heralded single-photon source through pump-degenerate spontaneous four-wave mixing (SFWM), exhibiting a spectral purity of P=0.67±0.05 and a heralded anti-bunching of g⁽²⁾ₕ(0)=0.0042±0.0015. Together, these results demonstrate both photon-generation schemes on a single integrated Si₃N₄ platform, highlighting its potential for scalable, tailored quantum light generation.