Maybe he felt trapped in the other relationship & he didn't want to have children with that person. My partner and I both said we never wanted this before one another. When you want to be with the person you're having the baby with it makes it so much better, it just makes you more in-love with them & the baby :-)
The relationship plays a huge part in how much attention and affection you show to each other. If they were always fighting and not in love anymore then of course it's different with u hun
It could be the love he has for you is different than what he has had with her... It makes a huge difference
Maybe he is fixing mistakes he made before? Or knows that its important he is involved.. i wouldntquestion him id be so happy!
How much he cares for his partner I'm sure is a big part of it.