When DS has a frustration tantrum, it's because he can reason HOW to do something but his body won't comply. He knows HOW to make a big duplo train, but connecting things, keeping them connected and the big tower not falling over while he moves the train is just too hard for his body.

So I encourage him to keep things smaller, within his capabilities. Or just hide the stupid train and get out an "easier" toy. Because he CAN do this, he's happier. Until someone else finds where I've hidden the Duplo and gets it out again.

Maybe something like that would work? He's frustrated because he CAN'T have Mama all to himself, so he works out how to make everyone else miserable (or it feels like that). But he can have this toy or this book all to himself - HE can choose to share and we all read together if he likes. Make time - maybe naptime - when it's just the two of you. Let your son know you love doing this with him and it's a shame it's not always like this - maybe when the baby wakes up he can join in? Or we can do something else all three of us. Up to you to pick. That way he has some choice in the matter and feels more in control and like he has more of your attention.

Best of luck to you.