Say exactly who and which you mean — que, quien, el cual, cuyo — out loud.
Default to que — it is the workhorse relative (el libro que leí anoche estaba buenísimo). The moment a preposition appears, Spanish keeps it with the pronoun: la silla en la que me senté estaba rota, never la silla que me senté — and for people, preposition + quien is the elegant C1 instinct (la profesora con quien estudié). Possession takes cuyo, agreeing with the thing possessed, not the possessor (el escritor cuyo libro ganó el premio), while el cual stays formal and written. And one comma changes everything: mis hermanos que viven en Lima means only those siblings; mis hermanos, que viven en Lima means all of them.
Below: the phrases each pronoun builds, the slips that are easy to fix, and a way to use them in a live spoken conversation — no flashcards, no fill-in-the-blanks.
Say this
Watch out
The part no drill site can do
Carla
Your grammar teacher for this pack
There are no flashcards in the Clarity Queen lessons and nothing to fill in — you talk, and Carla makes every pronoun earn its place. She asks where you grew up and you reach for donde; you mention work and need la empresa para la que trabajo; you describe a writer you admire, and the moment 'que su' slips out she catches it — possession is cuyo — and hands the moment back to you, out loud, until el proyecto del que te hablé rolls off without you thinking about the grammar at all.
Blank mid-sentence and nothing bad happens — she waits. That's the practice, without unnecessary judgement.
Quick answers
After a preposition. Spanish never strands the preposition — it travels with the relative: la empresa para la que trabajo, ese es el motivo por el que renuncié. Saying la ciudad que viví is the classic error; it's la ciudad en la que viví or la ciudad donde viví.
For people after a preposition — it sounds more elegant than el que: el amigo de quien te hablé, la persona en quien más confío. On its own, quienes lleguen tarde no podrán entrar belongs to formal, institutional Spanish.
It means whose, and it agrees in gender and number with the thing possessed, not the possessor: el escritor cuyo libro ganó el premio, es una empresa cuyos empleados están muy bien capacitados. Never substitute 'que su' — that's a calque from English.
Yes — in spoken LatAm Spanish it sounds stilted and bureaucratic. Reserve it for formal writing and non-restrictive clauses, especially when the antecedent is far away and clarity demands it: los datos sobre los cuales se basa el estudio son públicos.
The comma is meaning-bearing. Mis hermanos que viven en Lima vienen en diciembre = only the siblings who live there; mis hermanos, que viven en Lima, vienen en diciembre = all of them, and they happen to live there. Pause at the commas — don't rush through them.