They Call Me Mijo
I took notice of this a while back. My oldest sister and older brother call me mijo. My oldest sister is 9 years older than me and my older brother is 6 years older than me. The sister that 4 years older than me doesn't call me mijo. I think my oldest siblings do call her and also my younger brother mija and mijo, respectively.
I wonder if most families do this. We have always looked to my older siblings for guidance, for some reason. We still do. I just found it interesting that they use this as a term of affection.