Reaching out to baby daddy’s other baby mama

I’m 23 years old and 26 weeks pregnant with my first . My baby daddy is 26. After a year of seeing each other exclusively, I found out I was pregnant. We were both in love. Our relationship was stable and our jobs were stable, and even though it was unplanned, we were happy about it. Going into the relationship, I knew that he had a 2 year old son that lives out of state from a previous relationship. He goes to visit him every few months, and I’ve met him a few times.

We recently moved in together. I had spent the weekend unpacking everything into our new place. I found his cell phone he had had the first 4-5 months we were together. He said it was broken so he got a new one. I tried to charge it to make sure it was broken before I tossed it, but it ended up turning on. So, ya know. I snooped a lil 🧐

Well I ended up finding a conversation he had with his other baby mama about 4 months into our relationship. Basically, it was him BREAKING UP with her. 3 months into our new relationship, he was still leading on his baby mama, giving her hope that he’d move back & be with her.

But that’s not all.

She was 5 months pregnant at the time she sent this message (she sent him ultrasound pics), & based off of older messages, he knew she was pregnant before he left the state (so he knew when he met me).

Now his baby daughter is 5 months old, and I didn’t even know she existed until I found his old phone a couple of weeks ago.

Obviously, I confronted him about it. His excuses were pretty expected (they had been having issues & had been trying to break up with her for some time....he fell in love with me & was scared of losing me...he lead her on because he didn’t want to upset her while she was pregnant...)

She was blocked on his phone when I found it, & he broke his phone about 2 months after the breakup messages were sent. Those are the last messages from her in his phone, so I’m pretty sure he really did cut ties with her completely (at least romantically) after he broke up with her.

There are other messages after the last one with her, sent to her sister in regards to how his kids are & what they need, but none with his ex directly.

So obviously I felt betrayed, and stupid. I also felt horrible for his ex, and the part I played in ending their relationship.

I also, of course, don’t trust that he won’t do the same thing to me.

I immediately moved back into the room I had been renting with my friend, and I haven’t seen my baby daddy in person in two weeks (although he tries to see me everyday).

Idk what I’m going to do in regards to him. That is something I need to meditate on.

If I don’t end up staying with him though,

Is it my place to reach out to his ex to let her know that her kids will have a half sister?

I doubt she even knows I exist. She definitely doesn’t know I’m pregnant.

Im mostly scared of the thought of my daughter growing up and wanting a relationship with her half siblings, but not knowing her place.

I won’t lie to my daughter. Once she’s old enough, I think she has the right to at least know her half siblings exist.

In a perfect world, she could even have a relationship with them.

Idk how I should go about this, or if I should leave it be until the time comes that my daughter is old enough to understand.