Family friend Derek Tague says Biggers, who went by "Buck, " died unexpectedly at his Plymouth, Mass.

WSJ: 'Underdog' cartoon co-creator dies at 85

In 2008, they were adopted by Lisa and Tague Harding of Minnesota through the Amani Baby Cottage, one of the respected, religiously-affiliated orphanages.

CNN: Red flags wave over Uganda's adoption boom

Zach and Philip' adopted father, Tague Harding, understands that his sons will lose some of their cultural heritage by growing up in the United States, but he also sees the advantages.

CNN: Red flags wave over Uganda's adoption boom