Worst affected are passengers who have bought the cheapest deals. But even BA's executive club members who have been awarded 'companion vouchers' to go on a romantic break or honeymoon with their partner are being separated on flights.

The only way to ensure a seat with your family is to pay £20 to reserve one on longer flights of five hours or more, or £7 a seat on short-haul flights.

Split up: Furious travellers complain that they are being split up from loved ones as they head off on holiday. Worst affected are passengers who have bought the cheapest deals
Seats by the emergency exit cost £50 to reserve, while executive club members are charged £24 per seat on longer flights.

The policy was introduced in 2009. Paid-for reservations were said to be based on requests from customers – but many are now complaining about the policy on social media, as the airline also faces a backlash for scrapping free sandwiches on short-haul flights and for its plans to reduce leg room on some flights.
Source - http://www.dailymail.co.uk/news/article-4638270/British-Airways-asks-fee-guarantee-seats-together.html