I have 18 months apart with my 2.

DS1 is a bit jealous of DS2 needing to BF first and he always wants attention when I am feeding DS2 but generally he brings toys to me that I can help with with only 1 hand.

Make sure you dive child 1 lots of attention when 2 is asleep.
If DS1 beside me and i am holding DS2 i will give them both kisses often.

I put DS2 on DS1 knee and let him cuddle him, and always remind him to be gentle.

He follows me when i go and change DS2 nappies and when bathing DS2 DH holds DS1 up so he can watch and put his hands in baby bath.

Your older child will understand a lot more than mine as that much older. Have you got a book on bringing baby home??

Good luck and enjoy