Implies a gradual, often unintentional loss of connection between people. Even as siblings, they began to grow apart, sharing fewer interests.
Pro Tip 2/3
No Blame
Doesn't necessarily mean that someone is at fault for the change in relationship. There was no argument; they just slowly grew apart.
Pro Tip 3/3
Subtle Change
Indicates a process that may not be immediately obvious but occurs over time. The childhood friends didn't notice how they'd grown apart until their reunion.