I'm curious if you've intentionally (or subconsciously) been putting off the children thing until you're essentially done working ... so that, as a single parent, you could really experience every moment with your child(ren) and avoid daycare, avoid worries related to money/layoffs/etc., not be stressed out from work and juggling multiple roles, etc.
I imagine that the challenges of being a single parent can be somewhat alleviated by a solid support system (not sure if you have that available through family/friends) but that doesn't make it easy.
Also it's possible that on the journey to FI, you were searching for your passions and ways you wanted to spend your time once a job was removed from the equation ... and this thought kept creeping up in the back of your mind.
I can even see myself in your situation someday ... unfortunately there's no return policy and it's not like a hobby where you can simply give it up if you don't like it (well I guess you can, but that would be seriously screwed up), so I have been leaning strongly towards "no". Will I feel the same way in 8 years? I have no idea. Achieving financial freedom has been a driving force in my life ... although that may be different than the "personal" freedom you mentioned.
Have you always envisioned yourself as a parent, or did something recently trigger the desire to procreate?
Since you are still working ... is there an EAP (Employee Assistance Program) you can utilize to discuss these ideas with a therapist (if you're comfortable doing so)?