Breakdown of kazoku wa kanojo o kangeishita.
Questions & Answers about kazoku wa kanojo o kangeishita.
は marks the topic of the sentence.
So in 家族 は 彼女 を 歓迎した, 家族 is the thing the sentence is about: as for the family, they welcomed her.
In natural English, you usually would not translate は directly. It mainly helps organize the sentence. Here it tells you that the family is the topic, and the rest of the sentence says something about them.
