How will I marry him with his kids?

Good day ma and may God continue to bless you!
Am 26 in a relationship with a 33 years old guy, we have been dating for a year now, we both love each year other, he has three kids with a lady but not married to her yet, mean while I knew about his kids and the mother of the kids they all live together, but he is asking me to marry him. But my problem now is how will I marry him when he has kids and they all stay together, I asked him what he will happen to her and his children, he said he will settle her by giving her comfort and her needs, but am not okay with that and I asked him to marry her that people will laugh at me that am the reason he didn't get married to her, he said if I don't marry him he will still never marry her, that he never loved her he made kids with her cos of his mum, so my problem now is, I don't know what to do, if I should let go of him of still continue, am confused here
Dear sender,
If he made kids with her because of his mum, what made you feel that she will leave him or accept his settlement offer when his mum is still there to direct the affairs of his life?
If he does not love her, how then did he arrive at not one, not two but three kids? Was that out of praying and fasting?
And then he convinced you that he would never marry her yet they share the same bed, how marvelous?
Oh I forgot, what are the strategies you have devised to convince his mum that you are the lady God sent for his son?
Well, the choice is yours to make, at least you love him so I may only ask, are you sure your love can stand the heat in time to come?
Are you sure this romance will stand the test of time?
Are you really convinced that he is truly the man God has prepared for you?
Look well dear and clear yourself of the confusion before it turns to regrets.