Hopefully just hormones!? Feeling guilty over here.

Have any of you Mamas with older children, kids of friends/ family or stepchildren around randomly got protective over babys belongings?

I'm a Stepmum to a five year old and we have a great relationship. He's excited to meet his little brother and we made sure where possible that he's included and kept up to date with baby. He's gonna be an amazing big brother.

I'm not materialistic at all but I get antsy and irritated when he messes with the pram or babys clothes and stuff. I know he's not doing any harm and that it's totally irrational to get annoyed.

Is it hormonal? ( 38 weeks 3 days) Or do other people get like this about babys stuff? X