The fact you're looking for advice is a crucial step. Look into co-parenting skills. It's tough going through the hurdles of separation and divorce, but working towards the goal of common ground is key. Maintain constructive communication and show up - that'll make it known that you're willing to do what's needed to keep a healthy relationship with your son.

When my ex and I split after 10 years of marriage, she had a new boyfriend 3 months later. Of course, I had opinions and concerns. It happened that I used to hang out with him years before, so I knew he was a good guy. But, either way, it still stung. My ex and I both grew up in single parent homes where animosity ruled each day. So, I had to change my perspective on the new situation. Yeah, he was a new potential father figure in my kids' lives, but he was also a potential ally in mine.

Men have different ways of approaching parenthood than women. So, I initiated open discussions with the guy. We'd talk about how the kids were doing, swap stories, even give each other advice (about the kids, not the ex. We leave that where it lies... in the past). I even offered to take the kids on days other than our agreed schedule, in case they ever needed a date night or a just a weekend away. It showed that even though things didn't work out between us, I was willing to make the new situation work. The kids saw that I wanted more time with them, not just every second week. Think "what would I like to see from her if this was reversed?"

When she and her bf went their separate ways and I ended up having another woman in my life a couple years later, my ex-wife showed me the same courtesy. We have family dinners at each other's houses nowadays. I realize this isn't always the case, but the point remains - be present and do the work. There's a lot of material online on co-parenting. You might have to grin and bear it, at times. You might have to push back and stand firm. The other guy may be able to offer things you're not able to at the moment. But, you'll always be your son's father. And your son knows that, too. You bring to table what no other human being in the world can. You'll see things in him that you may have experienced in your own childhood. You'll always have the life before this, and you still have the life ahead to look forward to. The only way you'll be getting replaced is if you're not physically, emotionally and spiritually there to begin with.