We have 3 DC, DD 4.5, and 20 month old twins.
DH really, really bonded with DD from the begining pretty much, they have a special father/daughter bond.
We didn't see twins coming when we tried for baby number 2. It was an incredibly tough, busy time after they were born. Although I did find it hard initially to bond with the twins, and I almost cracked under the pressure, I think in the end its made me stronger and was delighted really the twins were so healthy etc and have become very sweet, easy going little men :)
DH works full time in a stressful corporate job and around the time the boys were born, he went through a bad time mentally. He said he flet trapped having 3 DC, he didn't feel like he'd bonded with the boys and just saw them as 'work' and felt overwhelmed with his life.
Thank god, things are much better now. DH has a lovely relationship with his DSs now, they light up when he comes home from work. 
But was just thinking, was my DH suffering from post-natal depression?