"They're unbelievable," Haven, 34, an activist for AIDS and human rights causes, tells Marie Claire in November's issue. "Zahara likes to hide from Angie, who always knows, right when she walks in the room, that Z's playing."
As for Pax, who was adopted at age 3 in March from a Vietnamese orphanage, the child "amazed me the first time he said my name," says the proud uncle.
"He didn't know any English, and I hadn't heard him say a word yet, so I wasn't expecting it," says Haven.
Human Rights ActivistHaven, an executive board member of Artivist, which is sponsoring an L.A. film festival Nov. 8 - 9 for movies about human rights and environmental issues, says he got started in philanthropy because of his sister.
"Angie was the catalyst," he says. "She'd say, 'I just heard this is going on in Darfur ...' and I'd want to be involved."
He also was prompted by what he called his difficult home conditions growing up with father Jon Voight.
"I don't want to constantly berate my father – I wish him well, and I hope he finds peace – but he put my mom through years of mental abuse, and it made me care especially for abandoned women and children," says Haven. "So that's my religion – helping widows and orphans."
A rep for Voight didn't return a call seeking comment.
On a less serious note, Haven says he still wishes people would forget about his famous kiss of his sister at the 2000 Oscars.
"So long ago!" he says. "Can we please move forward? Someday I'll get married, and on my wedding day they'll be saying, 'OK, we have to ask about that infamous Oscar kiss.'"