は自分の家族について

about one's own family

→ は
phrase Rare #37,406
about one's own family は marks the topic, while について means “about.” 自分の refers to the subject's own family.
JA: 彼は自分の家族について何も話さなかった。
EN: He didn't say anything about his family.

トムは自分の家族についてあまり話さない

Tom doesn't talk much about his family.

彼女は自分の家族について話をした

She talked about her family.

トムは自分の家族について一切話さない

Tom never talks about his family.

トムは自分の家族について話した

Tom talked about his family.