Standing in the driveway, I watched my grown children drive off into the distance. I looked down the road until I could no longer see their vehicles.
“They live too far away from me,” I said to myself.“When did they break away and become parents of small children? Shouldn't that be me?”
Does " break away" fit in the underlined part? I think they(=her children) break away (from the family) and become parents of small children.
Does "Shouldn't" make sense in the other context?
Which other context? Perhaps you mean 'in the other sense', but we can't answer that until we know what you regard as the primary one.