Legal Step to Undertake for Joint Custody from an Unwilling Live-in Partner?

My best regards to anyone reading this post.

I wish to ask for legal advice pertaining an issue of my fiancee's only son and his recalcitrant live-in partner.

Their relationship started over 12years ago but they have broken romantic ties 7years ago. They were never married however, they begot a son and have decided to continue to live together in order to provide a nuclear family setting for the child, now 8years old.

Recently, my fiancee expressed his desire to leave their household but the mother of the child threatened a sole custody battle for his son should he do so.

I would like to ask what steps should he take in order to assure legal joint custody of his only son.

Thank you for your time.

your fiancee still lives with him? are you based outside the philippines?

if they are not married, only she has the right to custody of the child.

my brother's girlfriend is pregnant and is now on her 5th month. Parati sila nagaaway and the girl always threatens him na tatanggalan sya ng right sa bata. Is there any way that we can file something para hindi ilayo sa knya ang anak nya?? i know you said earlier na ang custody ay sa mother when the couple is not married. we're not after custody though. we just want to see the child and that my brother can claim the baby as his kahit na ayaw ng babae. may habol ba kame dito?

if she refuses, he can file a petition for enforcement of his visitation rights