My 2 year old daughter gets along great with her newborn sister, and they’ve had some sweet moments. But my toddler has claimed dibs on every play mat, baby chair, and swing. The “mine” phase arrived quite suddenly, and sometimes with hilarious results (imagine a 3-foot-tall toddler’s legs just dangling from a baby rocker). Not complaining or asking for advice. Just sharing an anecdote to help this community start growing.
Welcome to the suck! Don’t worry, just as soon as you get used to something, it will change.