Steve, 44, who was killed by a stingray's barb on northern Australia's Great Barrier Reef on Monday, and Terri, 42, have two children: daughter Bindi, 8, and son Robert, who turns 3 in December.
Raines, who lives in Eugene, Ore., also said that Terri "told me, 'I'm very concerned about raising the children by myself,' but I know she'll do well."
Meanwhile, Steve Irwin's family has decided to hold a private funeral to be held within a week, and a public memorial service, which will be held within two weeks, with thousands expected, the Associated Press reports.
Irwin's father, Bob, said in a statement on Thursday that the family and "closest friends" would attend the private service, confirming that the "generous government offer" of a state funeral had been turned down.
Bob said his son wouldn't have wanted a formal state funeral because "he's an ordinary guy, and he wants to be remembered as an ordinary bloke."
No details were released about the location for a public memorial, but the Irwin family's 60-acre Australia Zoo and a nearby sports stadium in Brisbane have been mentioned.