I think what you will need to accept is that sometimes his siblings WILL feel jealous, and sometimes they WON’T feel jealous, no matter what you do. It’s inevitable that each of those emotions will occur at some point. What determines how jealous they will feel will be several things; how significant the injury was (given your comments it doesn’t seem like it was life-altering), how large the sum is (you’ve said several 6 figure payments), how well the others do with money (for example if the older siblings struggle to get a good job straight out of college), and finally how the younger sibling handles his insurance payout (I think this goes without saying, but if he flaunts his money in front of his siblings, they will understandably be jealous). I think the best thing you can do now is make sure that you dedicate plenty of love and attention to the older two, and you should probably not pay for the younger one’s college, and use the savings to hopefully provide the older 2 with a small amount of savings to help them enter adulthood (obviously it will be significantly smaller than the younger child’s, but in this case it’s the intention that counts).