Kate Middleton and Prince William marked a fresh start by moving to Forest Lodge, as Adelaide Cottage became "a place of pain," royal biographer Sally Bedell Smith tells PEOPLE.

The Prince of Wales, 43, grew up volunteering with his mom, the late Princess Diana, at the homelessness charity, The Passage. Now, decades later, William is bringing his and Kate Middleton’s son, Prince George, 12, along for the cause.