Sounds like your kids will be close, Dee My two cousins are 18 months apart and are perfectly at odds with each other - always at each other's throats and competing with each other, even though they both live in separate countries (complete with verbal barbs not befitting of a brother and sister relationship!), so somewhere along the line, their relationship wasn't fostered as carefully as it could have been (probably because 18 months later my aunt was pregnant for a third time, followed a year and a bit later with the next...at least there was a 5 year gap between the next one, and then a manageable 2 years - I say manageable cos she was just over 40 yo by then, with the first 3 being quite headstrong little people!). So, I don't think close age gap alone will have kids being close, emotionally, to one another. My sister and I are 23 months apart and we only became 'close' about 10 years ago, and I know of others, still, who have big age gaps and are close as all get out. I think people have kids close together just cos they like the idea, rather than predominantly because they want them to be emotionally close.
Enough musing, more studying and tidying! I'll have to be careful not to spend too much time on here today or nothing will get done - looks like today will hover between wet-weather program and study (it's threatening to rain, so can't take Oscar outside later during a study break!).
Well, here's to all the nutters who have kids close together :P