After DS1 we agreed we’d only have one (we had our reasons) but by the time he was about 12 months old I started getting quite broody. I bought up the topic if having a second baby but DH was adamant that he didn’t want one. I kept jokingly mentioning it every month (trying to be casual) but he never changed his stance.
After about 12 months of him still not agreeing I dropped my casual approach and talked to him seriously about having a second. I explained how much I wanted one, my reasons why, how I thought it could enrich ours and especially DS1’s life and why it meant so much to me. ended up getting quite upset as I told him that I couldn’t bear the thought of never being pregnant again or having a new born again and he started to see how important it was to me.
Ultimately he told me he would think about it and then a few weeks later he said that ok, we can try for a second. He was almost 34 years old at that point (me too) and he said that his only condition was that if I wasn’t pregnant but the time he was 35 then we stopped TTC as that was his cut-off point regarding being too old to be a new dad.
It took a while for me to get pregnant with Baby number 2 but I did eventually happen before DH hit 35 thankfully and then had a second son.
The boys are 5 and 2 now and the relationship they have is so very special - even my husband will now admit how glad he is that we had a second because he’s bought so much joy into our life and DS1’s life.
About 6-7 months ago I bought up the idea of having a third baby and his response was to get a vasectomy 
Why is your DH so adamant about now having a second?