The first quality I see in those who can sustain relationships, not just romantic, but relationships, in general, is that they are selective about the people they let into their lives.
One of you may need more emotional support at a given time.
Or depending on what is happening in your life one of you in the relationship may have a physical or mental setback which means the other partner now has to step up and do more.
The second thing he has done that stood out to me is he’s taking things slow.
Not because he’s some commitment-phobe, but because he understands that this relationship won’t be built in a day.
And the third quality that stands out to me is that they take responsibility for their feelings.
They function in a paradigm of partnership, fully understanding that to have a great whole they need to take responsibility for their half.
If you decide to move forward and date someone who has a child, slowly build a relationship with them to see if this dynamic works for you.
See how it feels when you spend time with them and their child.
Blending families is possible, but it doesn’t happen overnight, and there will be some flexibility needed by all parties to make it work.