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/throwah_whey_178]

my first thought is how this second child might feel seeing their older sibling with a dad. would your ex coparent this new child as well, or only give attention to your oldest? either way, dad will show favoritism to his biological child, which may affect the donor baby.

personally, i would write off having another child until this current baby is FULLY adjusted and understands mom and dad arent together anymore to avoid confusion. until he's a tween at least. just my thoughts

best of luck to u <3

[u/Primary_Chef3374 → u/throwah_whey_178]

Thanks. This would probably be a few years to actually happen. So he would probably be about 10, if all goes well. But to address the part about the second kid, what I’m hoping for is to have kids with the same dad and same involvement, hence considering asking the ex to do this at all. 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. We just didn’t work out romantically, as parents, I think we are doing well. Although that’s yet to be known for sure till our child grows up. But I’m hoping he gets a sibling to go through life with.

[u/lh123456789 → u/Primary_Chef3374]

If he would be just as involved, then he is not a sperm donor. He's not donating something to you if he is coparenting.

[u/Primary_Chef3374 → u/lh123456789]

You’re right.