In Spanish there are specific terms for most step-relatives (step-father/padrastro, step-mother/madrastra, step-son/hijastro, step-daughter/hijastra, step-brother/hermanastro, step-sister/hermanastra, step-grandfather/abuelastro, step-grandmother/abuelastra). But, to my knowledge, there is no specific term for “step-relatives” or one’s “step family” as a group.
Perhaps due to this fact, the expression “step-relatives” has often been mistranslated as parientes politicos or parientes por afinidad, (which are actually “relatives by marriage” or one’s “in-laws”), or as parientes adoptivos, when obviously no adoption is involved among step-relatives.
Thus, and for want of anything better, I render “step-relatives” descriptively as parientes derivados del vínculo matrimonial en segundas (o siguientes) nupcias.” But this is so, so wordy, and I would really welcome other ideas from fellow translators who have had to deal with this term in family law texts.
Léxico Jurídico Español-Inglés 
Wouldn’t the family of ones padrastro or madrastra be considered a pariente político? After all if it were not for the marriage of the step-parent to the biological parent, there would be no familial relationship.
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Hi, Jason. I discussed this many years ago with a Spanish anthropologist, and I don’t remember their being any conclusion as to how to express “step-relatives” in Spanish. But if used with their strictest meanings, I don’t think the relationships with one’s “familia política” (“in-laws”) can be equated with one’s step-family. As an example, my “padre político” (father-in-law; my spouse’s father) is not the same as my “padrastro” (the husband of my divorced mother) who from a kinship perspective is not one of my “in-laws” (member of my spouse’s family). But I would have to revisit this with a Spanish anthropologist to see if the terminology has evolved (divorce was only legalized in Spain in 1981).
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Still, wouldn’t the relatives of the padrastro or madrastra be considered parientes políticos? After all, there would be no familial relationship if it were not for the marriage of the step parent to the biological parent. Is the distinction between primeras nupcias y segundas nupcias necessarily implicit in the definition of pariente político?
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If the context allowed for reference to “step-family” rather than “step-relatives,” you might consider using “familia reconstituida” or “familia reconstruida.”
A bit of a stretch, but could be enough to get the point across.
I’ve also seen reference to “familiastros” (but only once, and it sounds a bit ridiculous) (https://eprints.ucm.es/44531/1/T39242.pdf)
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“Familia recompuesta” is often used in Spain with the sense of “blended family” (“familia formada por una pareja y los hijos de ambos de una unión anterior, donde conviven hijos que no tienen parentesco entre sí y los nacidos de la nueva unión”). Not really the same as “step-relatives”, and I’ve heard people object to the term because it may imply that previously their families were “descompuestas.”
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¿Qué tal acortar tu propia sugerencia?: parientes derivados de segundas (o ulteriores) nupcias
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Hi, Javier. That’s a good option, and it’s good to “see” you on the blog.
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