を自慢に思う

be proud of

→ を
phrase Rare #32,491
be proud of Used to express pride in a person, achievement, or possession. The thing one is proud of is marked with を.
JA: 彼が息子を自慢に思うのも無理はない。
EN: It is no wonder that he is proud of his son.

彼がを自慢に思うのもわかる

I can see why he’s proud of his daughter.

彼が息子を自慢に思うのも無理はない

It's no wonder he's proud of his son.

我々が自国の古い寺院を自慢に思うのは当然のことだ

It is only natural that we are proud of our country's ancient temples.

私は一度も学校に遅刻したことがないを自慢に思う

I'm proud that I've never been late for school.