Learn Spanish (Spain): Cuando seamos adultos, queremos criar a nuestros hijos. - When we are adults, we want to raise our children.

Because of the rule you are learning in this lesson! When cuando introduces an event that hasn't happened yet, the verb that follows must be in the present subjunctive. Since growing up to be adults is a future event, we use seamos.

Why is the main verb queremos in the present tense if this sentence is about the future?

While becoming adults is a future event, the desire to do this exists right now. The speakers currently want this future outcome, so queremos stays in the present indicative.

Why do we need the word a in criar a nuestros hijos?

This is the personal a. In Spanish, whenever the direct object of a verb is a specific person or a group of people (like nuestros hijos), you must put an a right before it.

I have learned that levantar means to raise. Why does this sentence use criar?

In Spanish, the word for to raise changes depending on what is being raised. criar is used specifically for raising or bringing up living things, like children, pets, or livestock. If you were physically lifting an object, you would use levantar.