To be worried about sibling rivalry?

[pandarific]

I'm 7 weeks and I have a little boy who'll be two and a half when the new baby arrives, all going well.

I was incredibly jealous of my sister as the eldest - partly due to my mum's pandering to her and the whole 'oh she's only small' style of her parenting, but also partly because I felt overlooked, I really remember it.

This is worrying me as I desperately want to avoid setting up any entrenched bad sibling dynamics - I want to give my children the best possible start, but tbh my 21 month old is already hard work (he is lovely but is not by nature placid and compliant) and today he got extremely jealous when my MIL and SIL were looking after him and her niece showed up with a baby. There were apparently tantrums, a lot of 'NO nana, no no no' when MIL was holding the baby, and the same with SIL.

Some people say their first born wasn't jealous at all - I was really hoping he'd be one of them! Asides from my reading 'Siblings without rivalry' and getting him 'there's a house inside my mummy' to read, what can I do? Any other books about transitioning toddlers to another baby, or any tips that worked at all? Constructive advice would be great, rather than horror stories.

I made a point of leaving the baby to cry a bit longer than I otherwise would have if it meant I could finish doing something with DC1. (Same age difference)
We had a box of baby toys. If he wanted what she was "playing" with, he was allowed to take it if he swapped it for something out of the baby box.
New things for him to do next to me on the sofa when bf.
Praise for helping.

Absolutely no advice I'm sorry OP but following as I am in a similar position ... am 28 weeks with #2 and my DS will be 34 months when he's born...
So far we've been talking about babies and families a lot and how lucky we will be to have another person in our family to love.
I'm making sure my DH is prepped to have the new baby as much as possible (,will be expressing milk etc) so that I can still have 1-1 time with DS.
My friend recommended a great book called "the second baby book" by Sarah Ockwell-Smith which helped me quite a bit but whatever way you look at it, I imagine there will be some hiccups along the way!

Reframe it from jealousy to a survival instinct. Some little ones that small are still in the process of mentally seperating their caregiver from themselves, and so in his mind the new baby is a threat to his literal life. It's not that the other kids are better siblings because they're not jealous, it's that they've been able to make that distinction earlier. The trick is to help your son make that connection too. You won't do that effectively through punishment.

@lukasiak I definitely don't want to have to punish at all. I've just asked on the gentle parenting thread actually how tf you're supposed to deal with defiant/dangerous behaviour while doing gentle parenting, because I haven't worked it out yet.

You are not your mother and your dc are not you and your sister.

Dh was really worried about bullying because he was very badly bullied by his elder brother but of course that didnt happen because a) we wouldnt have stood for it, unlike his mother who had a whole golden child thing going on, and b) ds1 is an easy going child who loves his brother.

It's good that you understand the dynamic from your childhood - you are definitely not doomed to repeat it.