When my 3rd baby was born (he's 8 months old now), my son was 6 1/2 and my daughter 4.
My older 2 love him SO MUCH!! They still constantly beg to hold him and kiss him etc etc allllllll the time. They love making him laugh, and run to get his dummy if he cries and they constantly say how much they love him and they're so glad we had him!!
When I put the older 2 to bed at night I've to bring baby and let him lie on their beds for 5 mins, they fight over who sits beside him at dinner table, they even consider it their jobs to hold his wee hands out of the way while I change explosive nappies!
Honestly, I think an age gap like that is sooo special as they are old enough to really appreciate and enjoy it. My first 2 were 2 years and 3 months apart and that was hard work whereas this is just a joy ��