Focus on the implicit motives of your loved ones, rather their behaviors.
Remember that a four-year old has trouble when enough is enough.
Remember that a four-year-old doesn’t know how to show love towards a baby: he has to learn that a baby doesn’t like the same as a seven-year-old or as a grown-up.
Remember that a four-year-old can be the sweetest person in the world, and still make a baby cry many times.
Remember that a four-year-old’s motives are the way they should be, ven though his actions don’t betray it.
Remember that a four-year-old will be five in the not too distant future.
And let him learn.