Unless it is life threatening/super urgent then the youngest takes priority - they are less able to wait or require more of your physical being then an older child.

Yes, this is how things pan out here. Much to the ire of the 6 year old, who is deep into "it's not fair" and "you love her more than me" territory.

DD2 will be 3 in a month however, and it has become much less of an issue these days.