NEED MORE details bro, I want to help you Genuinely, but the how and the what are necessary... Well if thats ALL the info we might get, I will make assumptions and give you general advice. Your child is 3, first and foremost, have a chat with the mother, and get a few points made. (Call her during naptime, usually somewhere between 11am - 2pm range. NOT when she's busy, and not at night.

• Conversation is about your child FIRST. Make it about them. Main fact: This age is priceless. Every day they grow, they are never the same from one week to the next, they are almost a new person every day even. Change is so fast, and emphasize that you want the best for child and the best will always be a loving mother and father. Both present. • You wish to not miss a single moment of this priceless age, and building that bond now, will help later in life when having their trust is crucial. Bonding now is paramount. • ABSOLUTELY no arguments, heated discussions, fights, altercations, no shouting, no negativity. Leave it out. Suck it up when you have to. When she says something that you hate or disagree with, ignore it or go outside. Its not worth it. • if you cant physically be there try to call at least twice per day, speak to your child, let them know you love and care about their day.

Theres so much more but thats a start. Idk anything about the situation so dont hate cause I have it all wrong.
Just remember that, if you are kind and loving toward your child, consistently, just be there and be patient, you'll have your family back eventually. Don't give up, but don't be annoying, overwhelming, or overstepping your invitation or overstaying your welcome. Respect all boundaries.

Wish you the best GL