Maximo loves having his brother Teddy for company, but my boys are not self-entertaining. They still look to me all day to amuse them.
The advantage: lots of love!
The disadvantage: it's double the work, double the expense. It's much more difficult to take 2 anywhere, and the boys dislike if I leave one behind (the one left at home isn't alone because grandpa is always here, but they both want to go out).