I continued the tradition with my kids (and now grandkids), and I make sure I have gifts for all of the siblings when attending birthday parties for other children with brothers/sisters close in age.
Last year, when my oldest grandson turned two, I bought him a tricycle. For his little sister, I bought a flip phone (that makes noise). It came with a key fob, that also makes noise. She was only 15 months old, so I didn't have to match the amount I spent, just the "wow factor" ... and for a 15 month old, a phone and key fob that make noise is pretty "wow"!
She loved the phone ... but so did her brother. Nevermind the fact that they have three other phones and an "ipad", that all make noise, that silly flip phone became the toy they both coveted and fought over.
One Saturday Thing 1, (tired of listening to them fight and cry over the cheapest toy they own!) said she had looked for another one, but couldn't find any. We flipped over the phone and looked for any information that would lead us to another one. A minute later, she said "I found it on Amazon. It will be here Monday!" True to their word, it was delivered on Monday.
The next Saturday, I handed both babies their own flip phone ... and they were elated! My grandson put his on the table next to him so that he could play with his newfound love ... Playdoh.
His sister saw the phone, relatively unguarded, and snapped it up. As happy as one phone made her, two phones gave her twice the delight!! However, even though he wasn't playing with it, he wanted it back.
I made her give him his phone back. She did ... but she did her best to let me know it was probably the worst thing that had ever happened to her in her whole life ... then hopped into her pink Cozy Couple and headed off to run errands.