In Pirkei Avos 5:21 it says "ben chamishim l'eitza," age 50 is the time to dispense advice. I've noticed that in any given scenario with a suggested action, there is a scenario which is almost exactly the same except that the ideal thing to do is the exact opposite of the suggested action. So although I have found certain things useful and I share them in the hopes they might be useful to you, bear in mind that they might actually not work at all in your case or be the opposite of what would be ideal for your situation.
My daughters are 5.5 years apart. There wasn't much conflict. I dutifully read Siblings Without Rivalry before Chana was born. It wasn't such an issue, though I'm sure I integrated the advice and that helped. Likewise, there are 6 years between Chana and Elazar. (Ironically, Chana played with Elazar more than Sarah ever played with Chana.) Then we were blessed rapidly with two more boys. Now we had three boys in row. Age differences: 2.5 years, and 17 months. I knew I had to get on top of my game regarding sibling rivalry because no longer was it going to be "I'm leaving the baby on the floor next to the computer while you play and going to take a shower."
This is looking like it's going to be a two part post. First I'll discuss techniques that I've been using, and then the next post will be the main thing I've been thinking about recently.
This is not usually practical or relevant to a lot of people, but I mention it because when I was about to give birth and my toddler was still nursing, I read up on it and saw mentioned, over and over, how it affected the sibling relationship positively, how close the children were from it. And since I, too, have noticed this, and I do think tandem nursing affected my first two boys' relationship positively, I bring it up now. My middle boy weaned himself while I was pregnant, and I am sure that had he had the experience of breastfeeding while holding the hand of his little brother and gazing into his eyes, it would have cut down on his aggression. Unfortunately it was not an option.
hovering, blocking, teaching "gentle"
These are the tried and true techniques of teaching a toddler to handle his infant sibling. Hover over the toddler whenever he comes near the baby; do not assume he will not hit or be rough. Be on standby to block any hits, pinches, squishing, etc. Take his hand and have him stroke the baby and make "nice." I think a lot of irritation and agitation can be cut out with proper vigilance, supervision, and prevention-- which is practically difficult and exhausting to do. But when I make it a priority I don't regret it. It's not fair to the older one to get angry at him for being unable to control his aggression when out of the two of us, I'm the one who is mature enough to control myself. ('Cept when I'm not...)
moving away without speaking or giving off disapproving body language
When the older sibling attacks the younger sibling, intervene by scooping up the aggressor and moving away. I don't say, "Don't hit your brother" or "we don't" or "it's not nice." I've found they know all that already and either they want to be aggressive or they can't control themselves. I don't bother to "teach" them not to. I just stop it.
I've written about these concepts and techniques a few times. It mainly involves only stepping in when there will be harm (blood, bruises etc.) and when the aggressor is not responding to genuine distress signals by easing up. I see my last post was about 2.5 years ago, and I am reporting now that they don't fight that much, they do get into physical conflict that ends pretty quickly, and the smacks are, from my observation, usually with a careful amount of force.
When I move the aggressor away (without criticizing or scowling or negative body language) I often ask if they want to wrestle or roughhouse or play out their aggressive energy. This has been hugely helpful in navigating their feelings.
assuming that a great deal of sibling rivalry is due to fighting for love of the parent
To be continued in the next post.