In a world where cultures intertwine and values collide, Europe stands as a beacon of radical social transformations. Here, traditional marriage is no longer the sole path to building a lasting emotional partnership. Amid cities embracing modernity and intellectual currents liberating individuals from the shackles of the past, long-term relationships outside marriage have emerged as a social phenomenon that intrigues researchers and sparks debate between advocates and critics. What fuels this shift? And how have European societies redefined the very concept of "family"?