Mine are 22 months apart but on is beginning of 2015 and the other is the end of 2016, mine are in yr4 and yr6
I think 20 months / 22 months it too small of a gap. You'll have a toddler and a baby at the same time, it can be really hard at times
My youngest was a lovely surprise I wasn't expecting, but it was never my intention to have them so close together. I wish I'd left it longer so I had more time one to one with each child, people tend to think their older child is more grown up than they actually are once they have a tiny newborn too
My friend has a 4 year gap between each of her children and it's worked our really nicely, each child gor a large chunk of time with just their mum while the others were at school ( or not born lol )