sus razones

his/her reasons

→ su
phrase Rare #26,528
his/her reasons Possessive phrase; the exact English pronoun depends on context. It can also mean 'their reasons' or 'your reasons' in formal address.
SP: Entiendo que tuvo sus razones.
EN: I understand that he had his reasons.

Todos tienen sus razones.

Everyone has their reasons.

— Battle Royale (2000)

Sus razones no son serias.

Their reasons aren’t serious.

— Retrato de una mujer en llamas (2019)

Pero reconozco que debe haber tenido sus razones.

But I admit he must have had his reasons.

Tom tenía sus razones para para quedarse en Boston.

Tom had his reasons for staying in Boston.

Ella nos explicó sus razones.

She explained her reasons to us.

Todo el mundo tiene sus razones.

Everyone has their reasons.

— Kung Fu Sion (2004)

Tiene sus razones.

He has his reasons.

— Los Tenenbaums. Una familia de genios (2001)

Diga sus razones.

State your reasons.

Como dijo A Gui, todo el mundo tiene sus razones.

As A Gui said, everyone has their reasons.

— Kung Fu Sion (2004)

Él tiene sus razones para quedarse allá.

He has his reasons for staying there.