When you double up object pronouns (a sentence like "He sent ME THEM" or
"She gave US THEM"), be careful with the word "se" as an indirect object:
1)"SE" MEANS "SE"
"Se" is reflexive, meaning "self" to express "himself", "themselves", etc.
Paco se los manda (A sí mismo).Paco sends himself them.
2)"SE" FOR "LE"
"Se" is not reflexive, and stands in for "le" to express "him", "her", or "you".
Paco Se los manda (A él).Paco sends him them.
Paco Se los manda (A ella).Paco sends her them.
Paco Se los manda (A usted).Paco sends you them.
3)"SE" FOR "LES"
"Se" is not reflexive, and stands in for "les" to express "them" or "you".
Paco Ses los manda (A ellos)Paco sends them them.
Paco Ses los manda (A ellas)Paco sends them them.
Paco Ses los manda (A ustedes)Paco sends you them.