ellos mantendrán

will keep, will maintain

m a n t e n ˈd ɾ a n → mantener
mantendr keep; maintain + án third-person plural future
verb · third plural · future indicative Rare #47,587
will keep, will maintain third-person plural (they/you all) future tense
SP: Mantendrán la calma durante la reunión.
EN: They will keep calm during the meeting.
Conjugation of mantener
Indicative future
SingularPlural
First mantendré mantendremos
Second mantendrás —
Third mantendrá mantendrán
Subjunctive future
SingularPlural
First mantendré mantendremos
Second mantendrás —
Third mantendrá mantendrán

Tom y María mantendrán su promesa.

Tom and Maria will keep their promise.

Y lo mantendrán tan impecable como los muslos de la Virgen María.

And they will keep it as flawless as the thighs of the Virgin Mary.

— Sin novedad en el frente (2022)

Mantendrán su promesa.

They will keep their promise.

Los agentes que hay con ustedes les mantendrán al corriente.

The agents who are with you will keep you informed.

— [REC] (2007)

Sounds similar to