I have had only two female Sims with Don Lothario. They were from completely different saves, so it may or may not influence your opinion on him, or not.
In one save, I had two female sims living as friends in the save, they were based on preexisting characters. For one female, I edited a baby for her, and then had her do the science baby route. The other sim I had get with Don Lothario. For multiple game plays I had him visit, get my other female sim pregnant, and then leave. He did visit his kids, and she let him stay a few nights, but he would leave. They had 5 kids together, which were 4 boys and a girl. I eventually had my female sim marry him, but for the most part they did their own thing, unless he wanted to visit.
In my other save, I just married him into the family, and had him have kids with the female sim. Haven't really played the save file too much, but he still seems interested in his kids.