I'm going to try to make a long story short.
I had always wanted DC. I was TTC with a partner up til I was 27 but in hindsight he was totally unsuitable (functioning alcoholic, very lazy, emotionally unavailable, head in sand approach to everything.)
I left and met someone else. He was a single dad with primary residency of his then 5yr old son. His ex had walked out to be with another man when DS was 3. He was disabled (major spinal problems plus hearing loss.)
I moved in and although we had always planned to TTC in good time (after marriage), our attempts were unsuccessful and we did not qualify for IVF in our NHS area. In the meantime we still had DS living with us and he had started to call me mum.
I asked if I could adopt DS as mine but birth mum would not agree. Bear in mind at this stage she hadn't seen him except for a few hours at a time when she visited her mum, over a 5 year period. She paid no maintenance either.
His dad and I split up and his dad moved a long way away but I still kept contact daily on the phone and every school holidays I would go and get him to stay with me.
Then his dad died. He initially came to me but then his birth mum got in touch and persuaded him that "things have changed" and he would be better off there. Having just lost a blood family parent, he accepted her lure.
2 years later after repeated domestic violence, and all sorts of child abuse, not bothering to send him to school, etc, I was finally successful in getting him back to live with me.
He may not be my blood relative. But as far as we're concerned, we are a team. He's 23 now and has a host of mental health problems from the treatment his birth parents gave him, but he knows that I will never give up on him, and vice versa.
TL;DR - don't rule anyone out. You may well not be capable of having biological DC so think about embracing a partner's family instead.