I found 1-2 my hardest jump.  It was when I realised first hand that you can't just replicate everything you've done for the first,  nor will your next child necessarily be anything like the first.  Kids are unique,  their likes,  dislikes,  issues etc are all different.  2-3 was the easiest jump.  3-4 was trickier,  you need to spread yourself thin sometimes.  4-5 kids was fine,  it was just the realisation that I'm older and sleep deprivation is not as easy as it was when I was younger! I have 19, 16, 11 & 10 year olds and then a 1.5 year old.  Hardest thing by far has been the teenage years - some kids are easy,  some kids definitely are not and I'd happily take 4 little kids over 1 teenager sometimes!