SRS, it looks as though they had a "your, mine, and ours" kind of family. Here's a little bit more which might explain:

The Bronsons (Bronson & Ireland) lived in a grand Bel Air mansion with seven children: two by his previous marriage, three by hers and two of their own. They also spent time in a colonial farmhouse on 260 acres in West Windsor, Vt.
       Ireland lost a breast to cancer in 1984. She became a spokesperson for the American Cancer Society and wrote a bestselling book, "Life Wish." She followed with "Life Lines," in which she told of her struggle to rescue her 27-year-old son, Jason McCallum Bronson, from drug addiction. He died of an overdose in 1989, and she died of cancer a year later.
       Bronson is survived by his wife, Kim, six children and two grandchildren.