Related Clues:

• Purrer on a lap
• Adoptee of a sort
• Litter box user
• Windowsill sunner
• Adoptee, perhaps
• Garfield, to Jon Arbuckle
• Socks, once, for Bill and Hillary Clinton
• Indoor sunbather
• Willow, to the Biden family
• Litter box user, maybe
• Scratching post user (Note the last 3 letters of this answer + ...)