"He loves his Mom."

Translation: Он любит свою маму.

[khutch39]

Почему не можно "его?" Я знаю, что свою лучше, но...

[DrejcKokosar]

You need to use pronoun свой, when the subject is the same as in the pronoun used. On example: Он видела ЕГО маму (it is not his mother, it's other man's mother). х Она видела СВОЮ маму (she saw her OWN mother).

[khutch39]

The sentence can mean either of those in english.

[KrICEtON]

This mechanism is diffetent in English and in Russion. "Он любит его маму" sounds ugly or vulgarly (Like "He loves mother of somebody". )

(My native language is Russian, so I'm sorry if I make mistakes in English :) )

[ulgane]

Yes that's true but in Russian it's different and I really think this should be added to the свой-section of this lesson:
when the subject of a sentence is 3rd person and you want to express in the same sentence that something is theirs, to infer the sense of ownership, свой is MANDATORY.

Like the person before mentioned, "Он любит его маму" means "He loves his (=a friend's/someone's/etc) mother, while "Он любит свою маму" means "He loves his (=his own) mother."

[khutch39]

My point is that the english sentence should specify whether its his own or some other boy's mother.