I finished a PhD while working full time with 3 young kids.
Feel free to reach out if you've been interested and I can share my experience with you.
(I tried doing a PhD while working full time, and quit the idea after 3 years.)
When things went smooth (accepted paper) I tried to roll that motivation forward as much as possible.
2 years was during COVID so I never really had to travel for classes which really saved time.
I did most of the coding and ideation on either paternity leave or holidays. Evenings were often running smaller experiments or eventually endless iteration of a paper.
My wife was great and helped me focus usually 8-11pm most nights and some weekends 1-4pm.
We don't live nearby any family and friends were not much help.