必ず 誕生日 を 覚えて います。kanarazu tanzyoubi wo oboete imasu.
(He) always remembers the birthday without fail.

Breakdown of kanarazu tanzyoubi wo oboete imasu.
いるiru
to exist; to stay; to have (used for living beings)
をwo
direct object particle
(お)誕生日(o)tanzyoubi
birthday
必ずkanarazu
definitely; necessarily; invariably
必ずexpresses a strong commitment or assurance that something will happen or is the case. It's often used to make promises or to express unwavering certainty.
覚えるoboeru
to remember; to memorize
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