I'd run for the hills to be honest.
My sibling is six months out of her marriage and only a month or so after separating bil started another relationship with a woman who claimed he felt a connection to unlike any other, and he also started making plans for the future with her, plans to live together and have more children, I lost a lot respect for him when he moved so fast without even allowing his children to process their parents splitting, he introduced her to the kids after just a few weeks of dating because he didn't think it fair he put his life "on hold".
Anyway after a few months of dating new "the one" he had a wobble and asked for "some space" and what that actually was, was him telling my sister he misses her madly and misses seeing their children every day and yes, having sex with her too while also keeping his new girlfriend on the back burner and texting and phoning her about his head being messed up. My sister thought they were trying again but bil was stringing then both along and thankfully she caught him on the phone telling new girlfriend he loved her after he'd just shagged my sister, she won't ever take him back now. .
It's now been about six months and since that first break he had from his girlfriend, he's needed space to "sort his head out" at least three times, which consists of him trying to get into my sisters knickers because he misses her. His girlfriend seems like a nice woman and I feel bad because he's playing her for an idiot and she deserves so so so much better.
He puts his girlfriend before his children regularly, my sister suggesting he not introduce someone he's only know a few months to the kids, so he stopped the 50/50 agreement and dropped to every other weekend. And even then, he can't spend four days a month without her there and the kids don't like it so he often cancels on them.
My sister has recently started dating someone, it's been a month of every other weekend dates because she is showing more sense than bil and has made it very clear to the bloke that things will be moving extremely slowly and she won't be committing to anything long term until she is divorced (bil is digging his heels in) and has spent enough time with him to know she can trust him around her children, and even when they get to the point of him meeting the kids, that's be done very very slowly too, her heart wants to plan a future with him because she really really likes him but she knows that's not the best thing for her children and she will always put them first.
The red flag with your boyfriend would be that he's keen to move so fast and make promises when he has a child in the mix, if he hasn't processed and gotten over the separation then his young child is likely struggling too, and if he's making such plans with you so soon, has she introduced you to his child?
Saying all that, I know a case where it has worked, fil met dhs stepmum three month after leaving mil, he didn't divorce mil until ten years later through laziness more than anything else. He took it slowly with stepmil though, it was at least a year before she was introduced to the kids and she was prepared to stay with her family every other weekend if the children didn't like her, her and mil actually ended up being friends and still are 30 years later, dhs step siblings would have sleepovers at mils so fil and stepmum could have weekends away but, and I think this is the key part, fil had no feelings for mil and mil had no feelings for him, their marriage had been over long before they separated. I think that's the key thing, your boyfriend has feelings because it sounds like he didn't want to split. He needs to process and get over that on his own. Therapy might help him. Him wanting space but also staying in touch with you sounds like he wants to keep you as an option which isn't fair on you.