There is 17 years between my 2 DC. My DS was 17 when DD was born. He was never keen on the idea, in fact he was very kind of whatever about it, mainly because he knew it was my decision.
I had brought up DS on his own from birth, and also wanted the 50/50 care, to be able to share this with my partner.
However, my relationship broke down, DS left home (mainly due, he says, to not wanting to share living space with DD) and I can't say they get along that well now, almost 4 and a half years down the road.
I have noticed a change in DS lately though, and it's not as bad as it was, but DS has definitely felt usurped in my affection by DD, even though I have done and said everything possible to make sure he didn't feel this way.
Imo, it probably didn't help that DS didn't like babies or children generally before I became pregnant. He was never particularly good with babies and has never shown an interest in them. I suppose I thought it would work out over time, only it didn't. 
I have probably just had an unfortunate experience between my 2 though.