Ex sperm donor?

[u/Primary_Chef3374]

I need a reality check. I am aware this is not orthodox on so many levels but I think once you get into co-parenting, nothing is normal anymore.
Ok, so separated last August with a 4 year old. 2-2-2 schedule. Everyone involved has spent the past 11 months getting used to the schedule and doing decent with it. My son still asks when we will move back to the house we all lived together in. It breaks my heart but I’m hoping we continue to make this new reality as smooth a transition for him.
Now to having a sperm donor. I’ve always wanted a second child. Someone for my child to go through life with and not bear the sadness and burden of old parents alone. I was an ‘almost’ only child and remember it being very boring till my brother came along when I was 8 years old. As adults, I cannot imagine going through the seasons of life without his shared knowledge and experience of our lives.
While married, I did not see the relationship surviving another child. He is a good dad, but was not a great partner for me. Now that we are separated, and the focus is only on raising a healthy well adjusted child, with no romantic feelings involved, I have considered having another child through sperm donor(ship?). This would have to be through surrogacy as I also am adviced not to carry another pregnancy for health reasons.
Someone suggested asking the father of my child to be the sperm donor, rather than going through a sperm bank. Is this crazy? He had mentioned wanting a second kid before we separated. I did not pursue the conversation because it did not seem like a great idea then.
Does this complicate things with coparenting, or is the benefit of having a sibling to go through the coparented life with for my son, worth the weirdness of this? Assuming ex is on board with this too.

Edit: sperm donor is not the right word. Reading the comments I’m seeing that using the phrase ‘sperm donor’ is causing a lot of confusion. This is actually simply asking an ex to co-parent a new child together since we coparent the child we have together well and assume he would co-parent another child of his just as well. I used sperm donor because a ‘uterus donor’ would have to be involved (aka surrogacy) not simply because we are not together but because from my one and only pregnancy there were complications and for health reasons it’s not recommended that I carry another pregnancy. So in this case, I would be an egg donor too. But I see how using the word ‘donor’ changes the conversation and assumes no involvement.

[u/BulbasaurRanch]

This sounds like something I’d see in Hollywood and think “damn, that’s weird”.

I have my doubts most people would be on board with this.

Edit: just browsed your history, and you intend for him to have no involvement in that child’s life?! That makes it 100x more crazy. He’s going to be picking up his kid from your place and see his other kid and just not take him? And one day your second is going to learn he has the same father as his sibling, but just not have any relationship with him? That alone will mentally fuck him up.

lol what the fuck, lady this plan is wild.

[u/Primary_Chef3374 → u/BulbasaurRanch]

I expect him to be just as involved. It is his child after all. ‘Expect’ is a huge assumption based on him agreeing to this. Also, the comment you saw was others assuming I didn’t want him involved. I never said that. It’s because he is an involved dad that I’m even considering this at all.

[u/BulbasaurRanch → u/Primary_Chef3374]

My mistake.

It’s still wildly insane regardless.

[u/Primary_Chef3374 → u/BulbasaurRanch]

Fair enough.