If a live-in partner's parents were to claim parental control over their child's custody, despite there being no marriage, what would be the legal outcome under the guardianship and wards act 1890?

Aarzoo ke din, yeh sawal mere dimag mein aata hai jab main night study karta hoon. Let's say there's no written cohabitation agreement and no formal separation deed. The live-in partner's parents argue that the child's upbringing would be better under their care, citing family ties and cultural values. On the other hand, the live-in partner claims to have been a responsible caregiver and has a strong bond with the child. Would the court grant custody to the grandparents or uphold the live-in partner's rights? What factors would be crucial in deciding this?